Interpenetrating polymer networks using blocked polyurethane/polyurea prepolymers for golf ball layers

ABSTRACT

The present invention is directed to a method of forming a golf ball that contains an interpenetrating polymer network, or IPN, which includes at least two polymeric systems, in one or more of the layers. The first polymeric system may include a polyurethane-based or polyurea-based system having blocked isocyanate groups and the second polymeric system may include an epoxy-based or acrylic-based system, wherein the two systems are polymerized or cured simultaneously or sequentially to form an IPN.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/900,460, filed Jul. 28, 2004, now pending, which is acontinuation-in-part of U.S. patent application Ser. No. 09/833,667,filed on Apr. 13, 2001, now pending, which is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The present invention is directed to a golf ball that contains aninterpenetrating polymer network, or “IPN,” formed from at least twochemically different polymeric components intertwined with each other.The IPN includes a blocked polymeric component and its respective curingagent, catalyst, and/or initiator. The method of forming a golf ballcontaining an IPN of the invention in one or more of golf ball layers isalso an aspect of the present invention.

BACKGROUND OF THE INVENTION

Golf balls are formed from a variety of compositions. For example, golfball covers may be formed from balata, a natural or synthetictrans-polyisoprene rubber, ionomer resins, a durable thermoplasticmaterial, or polyurethanes or polyureas, relatively soft thermoset orthermoplastic materials. Balata covered balls are favored by more highlyskilled golfers because the softness of the cover allows the player toachieve spin rates sufficient to more precisely control ball directionand distance, particularly on shorter shots. However, balata coveredballs are easily damaged, and thus lack the durability required by theaverage golfer.

Ionomer resins have more or less replaced balata as a cover material.Chemically, ionomer resins are a copolymer of an olefin and an α,β-ethylenically-unsaturated carboxylic acid having at least a portion ofthe acid groups neutralized by a metal ion, as disclosed in U.S. Pat.No. 3,264,272. Commercially available ionomer resins include, but arenot limited to, SURLYN® from DuPont de Nemours and Company, and ESCOR®and IOTEK® from Exxon Corporation. These ionomer resins aredistinguished by the type of metal ion, the amount of acid, and thedegree of neutralization. While these ionomers provide extremely durablecovers, however, the spin and feel are inferior compared to balatacovered balls.

Polyurethanes have also been recognized as useful materials for golfball covers since about 1960. Polyurethanes are the reaction product ofa polyisocyanate and a polyol cured with a hydroxy-terminated oramine-terminated curing agent. U.S. Pat. Nos. 3,147,324, 4,123,061, and5,334,673 are directed to methods of making golf balls having apolyurethane cover. The resulting golf balls are durable, while at thesame time maintaining the softer “feel” of a balata ball. However, golfball covers made from polyurethane have not, to date, fully matchedSURLYN® golf balls with respect to resilience or the rebound of the golfball cover, which is a function of the initial velocity of a golf ballafter impact with a golf club.

Polyureas have also been proposed as cover materials for golf balls. Forinstance, U.S. Pat. No. 5,484,870 discloses a polyurea compositionformed from the reaction product of an organic isocyanate and an organicamine, each having at least two functional groups. Once these twoingredients are combined, the polyurea is formed, and thus the abilityto vary the physical properties of the composition is limited. Likepolyurethanes, conventional polyureas are not completely comparable toSURLYN® golf balls with respect to resilience or the rebound or dampingbehavior of the golf ball cover.

In addition, epoxy resins and acrylate resins have been used in golfball compositions as compatibilizers. For example, WO 92/12206 disclosesa resin composition for golf balls formed from a polyester blockcopolymer and an ionomer resin, and also including an epoxy-containingcompound to improve compatibility between the two polymers. Theresultant compositions are purported to have improved delaminationresistance, flexibility and modulus of resilience, however, theinclusion of such epoxy-containing copolymers increases the meltviscosity of the resin compositions, which makes the compositionsunusable for certain molding applications. In addition, U.S. Pat. No.5,321,089 describes a compatibilizers that contains a small amount ofacrylate resins to be used in an ionomer-based golf ball covercomposition. The disclosed balls had durability properties superior tobalata-covered balls, but inferior to golf balls having covers formedfrom ionomer blends.

As shown above, the majority of conventional compositions for golf ballshave advantages and drawbacks when used in a golf ball layer. As such,golf ball manufacturers are continually searching for compositions thatdeliver an ideal balance for golfers of all skill levels withoutsacrificing performance benefits, manufacturing efficiencies, or feel.

Interpenetrating polymer networks, or IPNs, are occasionally used toimprove key physical properties or to aid in the compatibilization ofthe components of a polymer mixture or blend. For example, the use ofIPNs may assist in improving durability, e.g., improving fracturetoughness and microcracking resistance, and thermal and mechanicalperformance. Various IPNs are discussed in U.S. Pat. Nos. 5,648,432,5,210,109, and 4,923,934. For example, U.S. Pat. Nos. 4,128,600,4,247,578, and 4,342,793 disclose IPN technology for plastics based on atwo-component urethane system polymerized simultaneously with an acrylicmonomer. In addition, U.S. Pat. No. 4,923,934 discloses the formation ofan IPN from the reaction of a blocked urethane prepolymer, a polyol, andepoxy resin, and an epoxy-catalyzing agent, such as an anhydride for usein coating applications.

Therefore, it would be advantageous to use the IPN concept to form acomposition that capitalizes on the favorable properties, butcompensates for deficiencies, of individual polymeric systems typicallyused for golf ball components. In particular, it would be beneficial touse an IPN that utilizes several polymeric components, compatibilizers,and blocking agents in order to achieve a golf ball composition thatmaximizes beneficial properties and minimizes potential problems. Thepresent invention provides such compositions.

SUMMARY OF THE INVENTION

The present invention relates to an interpenetrating polymer network ina golf ball. In particular, the present invention relates to a method offorming a portion of a golf ball comprising the steps of providing atleast a first polymeric component and a second polymeric component, eachpolymeric component comprising at least one monomer, oligomer,prepolymer, or a combination thereof; sufficiently polymerizing eachpolymeric component sequentially or simultaneously to form a polymer orpolymer network; crosslinking each polymer or polymer network to theother polymer or polymer network to form an interpenetrating polymernetwork (“IPN”); and forming the IPN into the portion of the golf ball,wherein each polymeric component of the mixture is polymerized byexposing the mixture to at least one energy source, at least oneinitiator, or a combination thereof for a time sufficient to polymerizesaid polymeric component.

In another embodiment, the at least one energy source is selected fromthe group consisting of microwave radiation, infrared radiation, visibleradiation, ultraviolet radiation, x-ray radiation, gamma radiation,electron beam radiation and a combination thereof. In anotherembodiment, the at least one initiator is selected from the groupconsisting of a thermal free radical initiator, a photoinitiator, acationic initiator, and a mixture thereof.

In a preferred embodiment, the thermal free radical initiator isselected from the group consisting of an azo compound, a peroxide, apersulfate, a redox initiator, and mixtures thereof. In anotherpreferred embodiment, the photoinitiator is selected from the groupconsisting of a peroxide, an azo compound, quinine, benzophenone,nitroso compound, acyl halide, hydrazone, a mercapto compound, apyrylium compound, a triacylimidazole, an organophosphorus compounds, abisimidazole, a chloroalkyltriazine, a benzoate, a benzoyl compound, abenzoin ether, a benzil ketal, a thioxanthone, an acetophenonederivative, a ketone, a metallocene, a hexafluorophosphate salt, asulfonium salt, a diacrylate, a polyol, a pyrollidone, and mixturesthereof. In yet another preferred embodiment, the cationic initiator isselected from the group consisting of a Group IA organo compound, GroupIIA organo compound, aryl sulfonium salt, hexafluorometallic salt,Bronsted acid, Lewis acid, and mixtures thereof. Typically, theinitiator is present in an amount of greater than about 0.1 parts perhundred of total polymer component. Preferably, the initiator is presentin an amount from about 0.1 to about 15 parts per hundred of totalpolymer component.

In one embodiment, the polymerization of each polymeric component issubsequent or simultaneous with the crosslinking of each polymer orpolymer network to the other polymer or polymer network. In anotherembodiment, the first polymeric component is polymerized in the presenceor absence of at least a second polymeric component to form a firstpolymer or first polymer network. In yet another embodiment, the secondpolymeric component is polymerized in the presence of the firstpolymeric component or the first polymer or first polymer network toform a second polymer or second polymer network. In another embodiment,crosslinking of the first polymer or first polymer network to the secondpolymer or second polymer network occurs subsequently or simultaneouslywith the polymerization of the second polymeric component to form thesecond polymer or second polymer network. In yet another embodiment, thepolymerization of each polymeric component and the crosslinking of eachpolymer or polymer network to the other polymer or polymer networkoccurs simultaneously to form an IPN.

In one embodiment, the first polymeric component and the secondpolymeric component include monomeric, oligomeric or prepolymericprecursors of vinyl resins; polyolefins; polyurethanes; polyureas;polyamides; polyamide/polyurethane copolymers, polyamide/polyureacopolymers, epoxy-end-capped polyurethanes, epoxy-end-capped polyureas,polyamide/polyurethane ionomers, polyamide/polyurea ionomers, acrylicresins; olefinic rubbers; polyphenylene oxide resins; polyesters; blendsof vulcanized, unvulcanized or non-vulcanizable rubbers withpolyethylene, polypropylene, polyacetal, nylon, polyesters, or celluloseesters; or polymers or copolymers possessing epoxy-containing, orpost-polymerization epoxy-functionalized repeat units.

In a preferred embodiment, the method further comprises providing a golfball center; and disposing the IPN about the center to provide a portionof the golf ball. In another embodiment, the IPN is included in anintermediate layer disposed about the center. In another embodiment, theIPN is included in a cover layer disposed about the center.

The present invention is also directed to a method of forming a portionof a golf ball comprising the steps of providing a first polymericcomponent comprising at least one monomer, oligomer, prepolymer, or acombination thereof; sufficiently polymerizing the first polymercomponent to form a first polymer or first polymer network; providing asecond polymeric component comprising at least one monomer, oligomer,prepolymer, or a combination thereof; sufficiently polymerizing thesecond polymer component to form a second polymer or second polymer; andcrosslinking the first polymer or first polymer network with the secondpolymer or second polymer network to form an IPN.

In one embodiment, the first polymeric component is polymerized byexposing the first polymeric component to a first energy source, a firstinitiator, or a combination thereof for a time sufficient to polymerizethe first polymeric component. In a preferred embodiment, the firstenergy source is selected from the group consisting of microwaveradiation, infrared radiation, visible radiation, ultraviolet radiation,x-ray radiation, gamma radiation, electron beam radiation and acombination thereof. In another preferred embodiment, the firstinitiator is selected from the group consisting of a thermal freeradical initiator, a photoinitiator, a cationic initiator, and a mixturethereof. In one embodiment, the first initiator is present in an amountof greater than about 0.01 parts per hundred of the first polymericcomponent. In a preferred embodiment, the initiator is present in anamount from about 0.01 to about 15 parts per hundred of total polymercomponent.

In another embodiment, the second polymeric component is polymerized byexposing the second polymeric component to a second energy source, asecond initiator, or a combination thereof for a time sufficient topolymerize the second polymeric component. In a preferred embodiment,the second energy source is selected from the group consisting ofmicrowave radiation, infrared radiation, visible radiation, ultravioletradiation, x-ray radiation, gamma radiation, electron beam radiation anda combination thereof. In a more preferred embodiment, the second energysource is electron beam radiation.

In another preferred embodiment, the second initiator is selected fromthe group consisting of a thermal free radical initiator, aphotoinitiator, a cationic initiator, and a mixture thereof. In oneembodiment, the second initiator is present in an amount of greater thanabout 0.01 parts per hundred of the first polymeric component. In apreferred embodiment, the initiator is present in an amount from about0.01 to about 15 parts per hundred of total polymer component.

In one embodiment, the first polymeric component is polymerized in thepresence or absence of at least a second polymeric component to form afirst polymer or first polymer network. In another embodiment, thesecond polymeric component is polymerized in the presence of the firstpolymeric component or the first polymer or first polymer network toform a second polymer or second polymer network. In yet anotherembodiment, crosslinking of the first polymer or first polymer networkto the second polymer or second polymer network occurs subsequently orsimultaneously with the polymerization of the second polymeric componentto form the second polymer or second polymer network.

In one embodiment, the first polymeric component and the secondpolymeric component comprise monomeric, oligomeric or prepolymericprecursors of vinyl resins; polyolefins; polyurethanes; polyureas;polyamides; acrylic resins; olefinic rubbers; polyphenylene oxideresins; polyesters; blends of vulcanized, unvulcanized ornon-vulcanizable rubbers with polyethylene, polypropylene polyacetal,nylon, polyesters, or cellulose esters; or polymers or copolymerspossessing epoxy-containing, or post-polymerization epoxy-functionalizedrepeat units.

In one embodiment, the portion of the golf ball formed from the IPN is acore, intermediate layer or cover layer. In a preferred embodiment, themethod further comprises providing a golf ball center; and disposing theIPN about the center to provide a portion of the golf ball. In a morepreferred embodiment, the IPN is included in an intermediate layerdisposed about the center. In another more preferred embodiment, the IPNis included in a cover layer disposed about the center.

The present invention is also directed to a golf ball including at leastone layer, e.g., the cover layer, formed from an interpenetratingpolymer network including a first polymeric system including apolyurethane or polyurea prepolymer cured with a first curing agent,wherein the prepolymer includes an isocyanate having terminal isocyanategroups, a blocking agent, and a polyol or a polyamine; and a secondpolymeric system including a) an epoxy resin and a second curing agentor b) an acrylate resin and an initiator. At least about 80 percent ofthe terminal isocyanate radicals groups are preferably blocked. Forinstance, at least about 95 percent or more of the terminal isocyanategroups may be blocked. In one embodiment, at least about 97 percent ormore of the terminal isocyanate groups are blocked.

In this aspect of the invention, the blocking agent is selected from thegroup consisting of linear and branched alcohols; phenols and phenolderivatives; oximes; lactams; lactones; β-dicarbonyl compounds;hydroxamic acid esters; bisulfite addition compounds; hydroxylamines;esters of p-hydroxybenzoic acid; N-hydroxyphthalimide;N-hydroxysuccinimide; triazoles; substituted imidazolines;tetrahydropyrimidines; caprolactones; and mixtures thereof. For example,the blocking agent may be selected from the group consisting of phenols,branched alcohols, methyl ethyl ketoxime, ε-caprolactam, ε-caprolactone,and mixtures thereof.

In another embodiment, the second curing agent is selected from thegroup consisting of anhydrides, Lewis bases, amines, amides, Lewisacids, and mixtures thereof. The initiator may include benzoyl peroxide,t-amyl peroxide, or mixtures thereof.

The cover layer may include an inner cover layer and an outer coverlayer, and wherein the outer cover layer includes the interpenetratingpolymer network.

The present invention is also directed to a golf ball including a coreand a cover, wherein a portion of the golf ball is formed from aninterpenetrating polymer network including a first polymeric systemincluding an isocyanate having terminal isocyanate groups, a polyol oramine-terminated component, and a blocked, delayed action curative; anda second polymeric system including a) an acrylate resin and aninitiator or b) an epoxy resin and a curing agent. In one embodiment,the blocked delayed action curative includes methylene dianiline andsodium chloride having a deblocking temperature of about 175° F. toabout 350° F.

In another embodiment, the first polymeric system is saturated. Inanother embodiment, the first polymeric system further includes acatalyst including an organometallic compound, tertiary amine, orcombination thereof. When the second polymeric system is formedincluding an acrylate resin and an initiator, the initiator may includebenzoyl peroxide, t-amyl peroxide, or mixtures thereof. And, when thesecond polymeric system includes an epoxy resin and a curing agent, thecuring agent may be selected from the group consisting of anhydrides,Lewis bases, amines, amides, Lewis acids, and mixtures thereof.

In this aspect of the invention at least about 80 percent of theterminal isocyanate radicals groups are preferably blocked. Forinstance, at least about 95 percent or more, about 97 percent or more,or substantially all, of the terminal isocyanate groups may be blocked.

The golf ball may be of any construction. For example, in oneembodiment, the golf ball includes an intermediate layer, which may beformed of a thermoplastic material. In another embodiment, the portionincluding the interpenetrating polymer network includes the cover.

The present invention is further directed to a method of forming aportion of a golf ball including the steps of:

-   -   providing a first polymeric component including a polyurethane        or polyurea prepolymer having blocked isocyanate groups;    -   providing a second polymeric component including a) an epoxy        resin or b) an acrylate resin;    -   sufficiently polymerizing the first and second polymeric        components sequentially or simultaneously to form first and        second polymeric systems;    -   crosslinking each polymeric system to the other polymeric system        to form an interpenetrating polymer network (“IPN”); and    -   forming the IPN into the portion of the golf ball,    -   wherein each polymeric component of the mixture is polymerized        by exposing the mixture to an energy source, curing agent, or a        combination thereof for a time sufficient to polymerize the        polymeric component.

In one embodiment, at least about 80 percent, preferably about 90percent, of the isocyanate groups are blocked. In another embodiment,the step of forming the first polymeric component further includes thesteps of: providing an isocyanate having terminal isocyanate groups;providing a polyol or amine-terminated component; reacting theisocyanate and polyol or amine-terminated component to form aprepolymer; and blocking the terminal isocyanate groups. In yet anotherembodiment, the step of blocking the terminal isocyanate groups furtherincludes the steps of: providing a blocking agent; and blocking theterminal isocyanate groups with the blocking agent to form a blockedprepolymer.

In still another embodiment, the step of forming the first polymericcomponent further includes the steps of: providing an isocyanate havingterminal isocyanate groups; providing a blocking agent; reacting theisocyanate and blocking agent to form a half-blocked intermediate;providing a polyol or amine-terminated component; reacting thehalf-blocked intermediate with a polyol or amine-terminated component toform a prepolymer.

The step of sufficiently polymerizing the first and second polymericcomponents may further include providing a first curing agent for thefirst polymeric component and a second curing agent for the secondpolymeric component. When the second polymeric system is an acrylateresin and an initiator, the step of sufficiently polymerizing the firstand second polymeric components may further include providing a firstcuring agent for the first polymeric component and an initiator for thesecond polymeric component.

The blocking agent may include linear and branched alcohols; phenols andphenol derivatives; oximes; lactams; lactones; β-dicarbonyl compounds;hydroxamic acid esters; bisulfite addition compounds; hydroxylamines;esters of p-hydroxybenzoic acid; N-hydroxyphthalimide;N-hydroxysuccinimide; triazoles; substituted imidazolines;tetrahydropyrimidines; caprolactones; or mixtures thereof.

In this aspect of the invention, the at least one energy source isselected from the group consisting of microwave radiation, infraredradiation, visible radiation, ultraviolet radiation, x-ray radiation,gamma radiation, electron beam radiation and a combination thereof.

In one embodiment, the polymerization of each polymeric component issubsequent or simultaneous with the crosslinking of each polymericsystem to the other polymeric system. In another embodiment, thepolymerization of each polymeric component and the crosslinking of eachpolymeric system to the other polymeric system occurs simultaneously toform an IPN. In still another embodiment, the IPN included in a coverlayer disposed about a center.

The present invention is also directed to a method of forming a portionof a golf ball including the steps of:

-   -   providing a first polymeric component including an isocyanate, a        polyol or amine-terminated component, and a blocked, delayed        action curative;    -   providing a second polymeric component including an epoxy resin        or acrylate resin;    -   sufficiently polymerizing the first and second polymeric        components sequentially or simultaneously to form first and        second polymeric systems;    -   crosslinking each polymeric system to the other polymeric system        to form an interpenetrating polymer network (“IPN”); and    -   forming the IPN into the portion of the golf ball,    -   wherein each polymeric component of the mixture is polymerized        by exposing the mixture to an energy source, curing agent, or a        combination thereof for a time sufficient to polymerize the        polymeric component.

In one embodiment, the step of sufficiently polymerizing the first andsecond polymeric components further includes the steps of: elevating thetemperature to deblock the blocked, delayed action curative; andproviding a curing agent or initiator for the second polymericcomponent.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention can be ascertained fromthe following detailed description that is provided in connection withthe drawings described below:

FIG. 1 illustrates a golf ball including a center and a cover layerdisposed over the center, in which at least one of the center or thecover layer includes an IPN.

FIG. 2 illustrates a multi-layer golf ball including a center, anintermediate layer disposed over the center, and a cover layer disposedover the intermediate layer, in which at least one part of the golf ballincludes an IPN.

FIG. 3 illustrates a multi-layer golf ball including a core, anintermediate layer, and a cover layer disposed over the core, in whichat least one part of the golf ball includes an IPN.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to compositions including interpenetratingpolymer networks (IPNs) formed from two different polymer chains. TheIPNs may be formed using a blocked polyurethane prepolymer and an epoxyresin. In addition, an IPN of the present invention may be formed usinga blocked polyurea prepolymer and an acrylate functional resin. Eachsystem includes a curing agent for the prepolymer and a curingagent/catalyzing agent/initiator for the second polymeric component,i.e., the epoxy resin or acrylate functional resin.

The compositions of the invention may be used with golf balls of variousconstructions, e.g., one-piece golf balls, two-piece golf balls, ormultilayer golf balls having a center, at least one intermediate layerdisposed concentrically adjacent to the center, and at least one coverlayer.

The Compositions of the Invention

As briefly discussed above, the compositions of the invention include anIPN, which generally improve the compatibility of polymeric components.IPNs are formed when polymerizable compositions are independentlyreacted to form distinct, intertwining, continuous polymeric chains.Combining chemically different types of polymeric networks results inthe formation of resins having different properties. Theinterpenetrating polymer network produced exhibits properties that aredifferent from the individual constituent polymers. In accordance, theterm “interpenetrating polymer network” or “IPN”, as used herein, refersto two chemically different polymer chains intertwined with each other.

IPNs useful for the present invention may include two or more differentpolymers or polymer networks and can encompass any one or more of thedifferent types of IPNs listed and described below, which may overlap:

(1) Sequential IPNs, in which monomers or prepolymers for synthesizingone polymer or a polymer network are polymerized in the presence ofanother polymer or polymer network. These networks may have beensynthesized in the presence of monomers or prepolymers of the onepolymer or polymer network, which may have been interspersed with theother polymer or polymer network after its formation or cross-linking;

(2) Simultaneous IPNs, in which monomers or prepolymers of two or morepolymers or polymer networks are mixed together and polymerized and/orcrosslinked simultaneously, such that the reactions of the two polymernetworks do not substantially interfere with each other;

(3) Grafted IPNs, in which the two or more polymers or polymer networksare formed such that elements of the one polymer or polymer network areoccasionally attached or covalently or ionically bonded to elements ofan/the other polymer(s) or polymer network(s);

(4) Semi-IPNs, in which one polymer is cross-linked to form a networkwhile another polymer is not; the polymerization or crosslinkingreactions of the one polymer may occur in the presence of one or moresets of other monomers, prepolymers, or polymers, or the composition maybe formed by introducing the one or more sets of other monomers,prepolymers, or polymers to the one polymer or polymer network, forexample, by simple mixing, by solubilizing the mixture, e.g., in thepresence of a removable solvent, or by swelling the other in the one;

(5) Full, or “true,” IPNs, in which two or more polymers or sets ofprepolymers or monomers are crosslinked (and thus polymerized) to formtwo or more interpenetrating crosslinked networks made, for example,either simultaneously or sequentially, such that the reactions of thetwo polymer networks do not substantially interfere with each other;

(6) Homo-IPNs, in which one set of prepolymers or polymers can befurther polymerized, if necessary, and simultaneously or subsequentlycrosslinked with two or more different, independent crosslinking agents,which do not react with each other, in order to form two or moreinterpenetrating polymer networks;

(7) Gradient IPNs, in which either some aspect of the composition,frequently the functionality, the copolymer content, or the crosslinkdensity of one or more other polymer networks gradually vary fromlocation to location within some, or each, other interpenetratingpolymer network(s), especially on a macroscopic level;

(8) Thermoplastic IPNs, in which the crosslinks in at least one of thepolymer systems involve physical crosslinks, e.g., such as very stronghydrogen-bonding or the presence of crystalline or glassy regions orphases within the network or system, instead of chemical or covalentbonds or crosslinks; and

(9) Latex IPNs, in which at least one polymer or set of prepolymers ormonomers are in the form of lattices, frequently (though notexclusively) in a core-shell type of morphology, which form aninterpenetrating polymer network when dried, for example, as a coatingon a substrate (if multiple polymers or sets of prepolymers or monomersare in the form of lattices, this is sometimes called an“interpenetrating elastomer network,” or IEN).

The polymer chains may be crosslinked, however, no apparent chemicalbonding should occur between the polymer chains, i.e.,inter-crosslinking, with the exception of the occasional/accidentalcovalent bond. Thus, it should be understood that an IPN according tothe invention should not include a copolymer network. The term“copolymer network,” as used herein, can be defined as a single polymernetwork formed from two or more different types of monomers, oligomers,precursor packages, or polymers, during which network formation: a) thecrosslinking reaction(s) result(s) in the different types of polymers,oligomers, or precursors being sufficiently inter-crosslinked, i.e., thepolymers, oligomers, or precursors of one or more types are connected topolymers, oligomers, or precursors of the other different types, suchthat effectively one crosslinked network connecting all the differentmonomers, oligomers, precursors, or polymers is formed; b) thecontemporaneous or consecutive polymerization reaction(s) of all thedifferent types of monomers, oligomers, or precursors result(s) in twoor more different types of copolymers, which may themselves beoligomeric or polymeric and may be precursors to (an)other type(s) ofcopolymer(s), and which may then undergo inter-crosslinking reaction(s),as in a), between the different types of copolymers; c) thecontemporaneous or consecutive polymerization reaction(s) of all thedifferent types of monomers, oligomers, or precursors result(s) in asingle type of copolymer, which may itself be oligomeric or polymericand may be a precursor to another type of copolymer, and which may thenundergo a sufficient intra-crosslinking reaction, i.e., the copolymerchains of the single type are connected to other copolymer chains of thesame type, such that effectively a single crosslinked network connectingcopolymer chains is formed; or d) any combination thereof.

For example, a grafted IPN is distinguishable from a copolymer network,in that the inter-crosslinking of a grafted IPN is only occasional,resulting in relatively few cross-type polymer linkages, while theinter-crosslinking of a copolymer network occurs relatively frequently,resulting in a relatively large amount of cross-type polymer linkages.As a result, the copolymer network is effectively a single copolymernetwork, while the grafted IPN according to the invention may be lightlyinter-crosslinked but is effectively a combination of at least two,preferably co-continuous, polymer networks. Preferably, grafted IPNsaccording to the invention have a substantial lack of cross-type polymerlinkages, or inter-crosslinking. In the context of the presentinvention, a component that has a “substantial lack of” an item shouldbe understood to have less than about 20 percent, preferably to haveless than about 10 percent, more preferably to be substantially free ofthat item. As used herein, the phrase “substantially free of” means thatthere is less than about 5 percent, preferably less than about 2percent, and more preferably less than about 1 percent of that itempresent. Most preferably, it means that the component or composition iscompletely free of that item. In one embodiment, a layer containing agradient IPN according to the invention has a flexural modulus belowabout 5 ksi.

With the exception of grafted IPNs above, all forms of crosslinkingrecited in the descriptions of IPNs above should hereby be understood tobe intra-crosslinks, or same-type polymer linkages, i.e., crosslinksbetween polymer chains made from the same precursor package. Still,grafted IPNs predominantly contain intra-crosslinks, but also contain asmall amount of inter-crosslinks.

It should also be understood that an IPN according to the inventionshould not include a combination of an individual polymer and a polymernetwork of essentially the same type as the individual polymer, e.g., asingle type of homopolymer or copolymer, such as PMMA, that has been: a)incompletely crosslinked, such as by incorporation of an appropriateamount of diacrylate monomer; or b) incompletely or completelycrosslinked and then blended with uncrosslinked, neat PMMA, is notconsidered an IPN according to the present invention, despite itspossible characterization as a semi-homo-IPN. Such a combination isconsidered a partially-crosslinked, single-polymer network or system.

IPNs of the present invention contain two or more polymers, at least oneof which is crosslinked to form a network. In considering polymersuseful in golf balls of the present invention, examples includecrosslinked or uncrosslinked incarnations of any polymer capable ofbeing incorporated into an interpenetrating polymer network.Particularly exemplary polymers include, but are not limited to,polyurea, polyamide/polyurethane copolymer, polyamide/polyureacopolymer, epoxy-end-capped polyurethane, epoxy-end-capped polyurea,polyamide/polyurethane ionomers, polyamide/polyurea ionomers, urethanepolymers or copolymers, polymers made from an epoxy-containingprecursor, polymers having backbone or pendant ester groups, polyimidesor copolymers containing imide groups, polymers or copolymers containingsiloxane groups, polymers or copolymers containing silane groups,acrylate polymers or copolymers (including, but not limited to, mono-,di-, tri, and/or tetra-acrylates), alkyl acrylate polymers orcopolymers, alkyl alkyl-acrylate polymers or copolymers, for example,such as poly(methyl methacrylate) and the like, polyacrylic acids orpoly(alkyl-acrylic acids), including, but not limited to, monomers suchas acrylic acid or methacrylic acid, polymers or copolymers containingvinyl acetate repeat units, polymers or copolymers containing halogengroups, polymers or copolymers containing a uretdione group, polymers orcopolymers containing an oxazolidone group, or mixtures thereof. Otherexamples of useful polymers may include polymers or copolymerscontaining or made from a conjugated diene, polymers or copolymerscontaining a styrenic moiety, ionomeric polymers or copolymers, ormixtures thereof. Preferred first, second or more polymeric componentsinclude monomeric, oligomeric or prepolymeric precursors of vinylresins, polyolefins, polyurethanes, polyureas, polyamide and mixturesand copolymers thereof, such as those described in U.S. Pat. Nos.6,646,061, 6,645,091, 6,648,776, and copending U.S. patent applicationSer. No. 10/190,705, the entirety of which are incorporated herein.

In one embodiment, the IPN of the present invention includes a firstpolymeric system including a blocked prepolymer and a second polymericsystem including an epoxy resin or acrylate resin. The blockedprepolymer may be polyurea-based or polyurethane-based. The specifics ofthe polymeric system are discussed in more detail below.

When the second polymeric component is an epoxy resin, the blockedprepolymer is mixed with the second polymeric component in the presenceof a curing agent/catalyzing agent and a short chain amine-terminatedcomponent or a short chain hydroxy-terminated component. For example,once the mixed material is heated to the temperature necessary fordeblocking the isocyanate groups, the prepolymer reacts with the shortchain amine-terminated component or short chain hydroxy-terminatedcomponent to form a cured polyurea-based system or polyurethane-basedsystem. At the same time, the epoxy system reacts with the curingagent/catalyzing agent to form a cured epoxy system. The two curedsystems form an IPN.

In the alternative, a “deblocking” agent may be added to the mixedmaterial to react with the blocked isocyanate groups, which allows theprepolymer to react with the curing agent to form a cured polyurea-basedsystem or polyurethane-based system. The epoxy system simultaneously orsequentially reacts with its respective curing agent/catalyzing agent toform a cured epoxy system. The two cured systems form an IPN accordingto the present invention.

Likewise, when the second polymeric component is an acrylic resin, theblocked prepolymer is mixed with the second polymeric component in thepresence of an initiator to cure the second polymeric component and ashort chain amine-terminated component or a short chainhydroxy-terminated component to cure the prepolymer.

In the alternative, an excess of the short chain amine-terminated orhydroxy-terminated component may be included in an amount sufficient tocure both the first and second polymeric components (instead of using aseparate curing agent/catalyzing component for the second polymericcomponent) for either type of IPN, i.e., an IPN including an epoxysystem or an IPN including an acrylic resin system.

It is important to note that when a short chain hydroxy-terminatedcomponent is used as a curing agent for a polyurea-based prepolymer, theresulting polyurea-based system will contain urethane linkages as aresult of the excess isocyanate reacting with the hydroxy groups of thecuring agent. Thus, for the purposes of the present invention, such asystem is referred to as a polyurea-urethane system as opposed to apolyurea system, which contains only urea linkages. Likewise, apolyurethane prepolymer cured with an amine-terminated curing agent willproduce a system including both urethane and urea linkages and will thusbe referred to as a polyurethane-urea system. Examples of suitablecuring agents/catalyzing agents for the epoxy resin, initiators for theacrylic resins, and amine-terminated and hydroxy-terminated curingagents for the prepolymer will be discussed in greater detail below.

The First Polymeric System

A blocked urethane or urea prepolymer may form the first polymericsystem of an IPN of the present invention. In particular, the urethaneor urea can be blocked to prevent premature polymerization orcrosslinking of the polyisocyanate groups. Because the two polymericsystems of the IPN may be cured simultaneously, the isocyanates groupsmay be subjected to heat to deblock the isocyanates once the prepolymercuring agent and curing agent/catalyzing agent/initiator are added tocure the two polymeric systems and form the IPN. In the alternative, a“deblocking” agent may be used to react with the blocked isocyanategroups in order to allow the isocyanate groups to react with the curingagent to form the first polymeric system.

In the context of the present invention, the term “prepolymer” refersgenerally to a macromonomer or partially polymerized material formed bythe reaction product of at least two components, each having afunctionality that is reactive with at least one other component underthe appropriate circumstances, which macromonomer or partiallypolymerized material can be subsequently reacted with at least one othercomponent (which may be the same as one of the at least two componentsor different) to form a polymer. In particular, a “prepolymer” may referto a material containing at least one isocyanate-containing componentand at least one isocyanate-reactive component, for example, such as apolyol, a polyamine, an epoxy-containing compound, or a mixture thereof.Alternatively, “prepolymers” according to the present invention may notinclude an isocyanate-containing component.

As briefly mentioned above, the prepolymer used in this aspect of theinvention may be a polyurethane prepolymer or a polyurea prepolymer. Thepolyurea prepolymer is the reaction product of an amine-terminatedcomponent and an isocyanate, whereas the polyurethane prepolymer is thereaction product of a hydroxy-terminated component and an isocyanate.The particular components of the prepolymers will be discussed ingreater detail below.

Because the main difference between the polyurea prepolymer and thepolyurethane prepolymer is the amine-terminated component/polyolcomponent, the isocyanates discussed are intended to be used in eithertype of prepolymer.

The Isocyanate Component

Any isocyanate having two or more isocyanates groups, e.g., two to fourisocyanate groups, bonded to an organic radical, may be used in theprepolymers of the present invention. The general formula of a suitableisocyanate for use with the present invention is as follows:R—(NCO)_(x)where R may be any organic radical having a valence x. In oneembodiment, R is a straight or branched hydrocarbon moiety, acyclicgroup, cyclic group, heterocyclic group, aromatic group, phenyl group,hydrocarbylene group, or a mixture thereof. For example, R may be ahydrocarbylene group having about 6 to about 25 carbons, preferablyabout 6 to about 12 carbon atoms. In another embodiment, R isunsubstituted or substituted. For example, in some cases, the cyclic oraromatic group(s) may be substituted at the 2-, 3-, and/or 4-positions,or at the ortho-, meta-, and/or para-positions, respectively.Substituted groups may include, but are not limited to, halogens,primary, secondary, or tertiary hydrocarbon groups, or a mixturethereof.

Because light stability of the compositions of the invention may beaccomplished in a variety of ways for the purposes of this application,i.e., through the use of saturated components, light stabilizers,whitening agents, or a mixture thereof, the isocyanate used in theprepolymer may be saturated, semi-saturated, unsaturated, or a mixturethereof. For example, isocyanates for use with the present inventioninclude aliphatic (saturated), cycloaliphatic, aromatic aliphatic(semi-saturated), aromatic (unsaturated), any derivatives thereof, andcombinations of these compounds having two or more isocyanate (NCO)groups per molecule. The term “saturated,” as used herein, refers tocompositions having saturated aliphatic and alicyclic polymer backbones,i.e., with no carbon-carbon double bonds. As used herein, aromaticaliphatic compounds should be understood as those containing an aromaticring, wherein the isocyanate group is not directly bonded to the ring.One example of an aromatic aliphatic compound is a tetramethylenediisocyanate (TMXDI).

The isocyanates may be organic polyisocyanate-terminated prepolymers,low free isocyanate prepolymer, and mixtures thereof. Theisocyanate-containing reactable component may also include anyisocyanate-functional monomer, dimer, trimer, or polymeric adductthereof, prepolymer, quasi-prepolymer, or mixtures thereof.

Examples of isocyanates that can be used with the present inventioninclude, but are not limited to, substituted and isomeric mixturesincluding 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanate (MDI);3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI); toluene diisocyanate(TDI); polymeric MDI; carbodiimide-modified liquid 4,4′-diphenylmethanediisocyanate; para-phenylene diisocyanate (PPDI); meta-phenylenediisocyanate (MPDI); triphenyl methane-4,4′- and triphenylmethane-4,4″-triisocyanate; naphthylene-1,5-diisocyanate; 2,4′-, 4,4′-,and 2,2-biphenyl diisocyanate; polyphenylene polymethylenepolyisocyanate (PMDI) (also known as polymeric PMDI); mixtures of MDIand PMDI; mixtures of PMDI and TDI; ethylene diisocyanate;propylene-1,2-di isocyanate; tetramethylene-1,2-diisocyanate;tetramethylene-1,3-diisocyanate; tetramethylene-1,4-diisocyanate;1,6-hexamethylene diisocyanate (HDI); octamethylene diisocyanate;decamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate;2,4,4-trimethylhexamethylene diisocyanate; dodecane-1,12-diisocyanate;dicyclohexylmethane diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;cyclohexane-1,4-diisocyanate; methylcyclohexylene diisocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanedi isocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′ dicyclohexylmethanediisocyanate (H12MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; 1,2-, 1,3-, and 1,4-phenylenediisocyanate; aromatic aliphatic isocyanate, such as 1,2-, 1,3-, and1,4-xylene diisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, and mixturesthereof; dimerized uretdione of any polyisocyanate, such as uretdione oftoluene diisocyanate, uretdione of hexamethylene diisocyanate, andmixtures thereof; modified polyisocyanate derived from the aboveisocyanates and polyisocyanates; and mixtures thereof.

Of the list above, the following isocyanates are saturated: ethylenediisocyanate; propylene-1,2-diisocyanate; tetramethylene diisocyanate;tetramethylene-1,4-diisocyanate; 1,6-hexamethylene diisocyanate (HDI);octamethylene diisocyanate; decamethylene diisocyanate;2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylenediisocyanate; dodecane-1,12-diisocyanate; dicyclohexylmethanediisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-di isocyanate;cyclohexane-1,4-diisocyanate; methylcyclohexylene di isocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanediisocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′-dicyclohexylmethanediisocyanate (H12MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; and mixtures thereof. Aromaticaliphatic isocyanates may also be used to form light stable materials.Examples of such isocyanates include 1,2-, 1,3-, and 1,4-xylenediisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, and mixturesthereof; dimerized uretdione of any polyisocyanate, such as uretdione oftoluene diisocyanate, uretdione of hexamethylene diisocyanate, andmixtures thereof; a modified polyisocyanate derived from the aboveisocyanates and polyisocyanates; and mixtures thereof.

The Polyol or Polyamine

A polyurethane prepolymer is the reaction product of an isocyanate and apolyol. Exemplary polyols include, but are not limited to, polyetherpolyols, polycaprolactone polyols, polyester polyols, polycarbonatepolyols, hydrocarbon polyols, and mixtures thereof. Both saturated andunsaturated polyols are suitable for use with the present invention.

Suitable polyether polyols for use in the present invention include, butare not limited to, polytetramethylene ether glycol (PTMEG); copolymerof polytetramethylene ether glycol and 2-methyl-1,4-butane diol (PTG-L);poly(oxyethylene) glycol; poly(oxypropylene) glycol; ethylene oxidecapped (polyoxypropylene) glycol; poly (oxypropylene oxyethylene)glycol; and mixtures thereof.

Suitable polycaprolactone polyols include, but not limited to,diethylene glycol initiated polycaprolactone; propylene glycol initiatedpolycaprolactone; 1,4-butanediol initiated polycaprolactone; trimethylolpropane initiated polycaprolactone; neopentyl glycol initiatedpolycaprolactone; 1,6-hexanediol initiated polycaprolactone;polytetramethylene ether glycol (PTMEG) initiated polycaprolactone;ethylene glycol initiated polycaprolactone; dipropylene glycol initiatedpolycaprolactone; and mixtures thereof.

Suitable polyester polyols include, but not limited to, polyethyleneadipate glycol; polyethylene propylene adipate glycol; polybutyleneadipate glycol; polyethylene butylene adipate glycol; polyhexamethyleneadipate glycol; polyhexamethylene butylene adipate glycol;ortho-phthalate-1,6-hexanediol polyester polyol; polyethyleneterephthalate polyester polyols; and mixtures thereof.

Examples of polycarbonate polyols that may be used with the presentinvention include, but is not limited to, poly(phthalate carbonate)glycol, poly(hexamethylene carbonate) glycol, polycarbonate polyolscontaining bisphenol A, and mixtures thereof.

Hydrocarbon polyols include, but not limited to, hydroxy-terminatedliquid isoprene rubber (LIR), hydroxy-terminated polybutadiene polyol,hydroxy-terminated polyolefin polyols, hydroxy-terminated hydrocarbonpolyols, and mixtures thereof. Other polyols that may be used to formthe prepolymer of the invention include, but not limited to, glycerols;castor oil and its derivatives; Polytail H; Polytail HA; Kraton polyols;acrylic polyols; acid functionalized polyols based on a carboxylic,sulfonic, or phosphoric acid group; dimer alcohols converted from thesaturated dimerized fatty acid; and mixtures thereof.

By using polyols based on a hydrophobic backbone, the polyurethanecompositions of the invention may be more water resistant than thosepolyurethane compositions having polyols without a hydrophobic backbone.Some non-limiting examples of polyols based on a hydrophobic backboneinclude hydrocarbon polyols, hydroxy-terminated polybutadiene polyols,polyethers, polycaprolactones, and polyesters.

Polyurea prepolymers are the reaction product of an amine-terminatedcomponent and an isocyanate. Any amine-terminated compound available toone of ordinary skill in the art is suitable for use in the polyureaprepolymer. The amine-terminated compound may include amine-terminatedhydrocarbons, amine-terminated polyethers, amine-terminated polyesters,amine-terminated polycarbonates, amine-terminated polycaprolactones,copolymers of polycaprolactone and polyamines, amine-terminatedpolyamides, and mixtures thereof. The amine-terminated segments may bein the form of a primary amine (NH₂) or a secondary amine (NHR).

Additional amine-terminated compounds useful in forming the polyureaprepolymers of the present invention include, but are not limited to,poly(acrylonitrile-co-butadiene); poly(1,4-butanediol)bis(4-aminobenzoate) in liquid or waxy solid form; linear and branchedpolyethylenimine; low and high molecular weight polyethylenimine havingan average molecular weight of about 500 to about 30,000; poly(propyleneglycol) bis(2-aminopropyl ether) having an average molecular weight ofabout 200 to about 5,000; polytetrahydrofuran bis(3-aminopropyl)terminated having an average molecular weight of about 200 to about2000; and mixtures thereof, all of which are available from Aldrich ofMilwaukee, Wis.

Blocking the Isocyanate Groups

As briefly mentioned above, the isocyanate groups in the prepolymer arepreferably blocked as a result of the reaction of a suitable isocyanatewith a blocking agent. The blocking agent may be any suitable blockingagent that results in the prevention of premature polymerization orcrosslinking of the isocyanate group(s) in the prepolymer.

Suitable blocking agents include, but are not limited to, linear andbranched alcohols; phenols and derivatives thereof, such as xylenol;oximes, such as methyl ethyl ketoxime; lactams, such as ε-caprolactam;lactones, such as caprolactone; β-dicarbonyl compounds; hydroxamic acidesters; bisulfite addition compounds; hydroxylamines; esters ofp-hydroxybenzoic acid; N-hydroxyphthalimide; N-hydroxysuccinimide;triazoles; substituted imidazolines; tetrahydropyrimidines;caprolactones; and mixtures thereof. In one embodiment, the blockingagent is selected from the group consisting of phenols, branchedalcohols, methyl ethyl ketoxime, ε-caprolactam, ε-caprolactone, andmixtures thereof.

In this aspect of the invention, preferably greater than about 80percent of the isocyanate radicals are blocked, and more preferablyabout 90 percent or greater of the isocyanate radicals are blocked. Inone embodiment, about 95 percent or more of the isocyanate radicals areblocked. In another embodiment, about 97 percent or more of theisocyanate radicals are blocked. In still another embodiment,substantially all of the isocyanate radicals are blocked.

The blocked isocyanate compound is stable at room temperature as acarbamic acid compound free of isocyanate radicals capable of liberatingat room temperature. When heated, or reacted with a “deblocking” agent,the isocyanate radicals are activated, i.e., deblocked and dissociated.For example, in one embodiment, the isocyanate group(s) is blocked withε-caprolactone. The ε-caprolactone volatilizes at a temperature ofapproximately 300° F., exposing the polyisocyanate groups forcrosslinking.

The reaction of the isocyanate and blocking agent may be accomplished inany suitable way that results in a blocked prepolymer. For example, theisocyanate groups may be blocked after the prepolymer is formed. Oneexample of such a blocking mechanism using a polyurea prepolymer isshown below:

where R and R₁ may be independently any straight or branched hydrocarbonmoiety, acyclic group, cyclic group, heterocyclic group, aromatic group,phenyl group, hydrocarbylene group, or a mixture thereof.

In particular, a blocked polyurea prepolymer may be formed by firstreacting a polyamide-based amine and an excess of isocyanate to form apolyamide-based polyurea prepolymer and then blocking the prepolymerwith a phenol to form a blocked polyamide-based polyurea prepolymer. Thegeneral reaction scheme is as follows:

where R may be independently any straight or branched hydrocarbonmoiety, acyclic group, cyclic group, heterocyclic group, aromatic group,phenyl group, hydrocarbylene group, or a mixture thereof.

A blocked polyurethane prepolymer may be formed in a similar manner,using a hydroxy-terminated component in place of the amine-terminatedcomponent. A general reaction scheme is shown below:

where R and R₁ may be independently any straight or branched hydrocarbonmoiety, acyclic group, cyclic group, heterocyclic group, aromatic group,phenyl group, hydrocarbylene group, or a mixture thereof.

The blocking mechanism may also be performed prior to the formation ofthe prepolymer. For example, a diisocyanate having isocyanate radicalswith different reactivities, such as 2,4-toluene diisocyanate, may beused to form a half-blocked intermediate. The half-blocked intermediateis then reacted with an amine-terminated component to form a polyureaprepolymer or a polyol to form a polyurethane prepolymer. The blockingagent used to form the half-blocked intermediate may be any suitableblocking agent. One specific example includes the use of equal parts of2-ethylhexanol and 2,4-toluene diisocyanate.

In addition, commercially available urethane and urea elastomers withblocked isocyanate groups are contemplated for use as the firstpolymeric system of the invention. For example, ADIPRENE® BL-16,commercially available from Crompton Corporation of Middlebury, Conn.,is a liquid urethane elastomer with blocked isocyanate curing sites thatcan be activated by heating. The blocking agent is methyl ethylketoxime. The free isocyanate content is less than 0.25 percent byweight.

The Curing Agent

The prepolymers of the present invention may be cured with ahydroxy-terminated curing agent, an amine-terminated curing agent, or amixture or hybrid thereof, which may include one or more saturated,unsaturated, aromatic, and cyclic groups. Additionally, thehydroxy-terminated and amine-terminated curatives may include one ormore halogen groups.

“Curing agents,” as used herein, means any compound, or combinationthereof, capable of connecting at least two polymeric or oligomericchains, precursors, or macromonomers together under appropriatecircumstances. For example, in step-growth or condensation polymers,e.g., such as the polyurethane-based or polyurea-based systems of thepresent invention, a curing agent may serve to build the linearmolecular weight of a single polymer molecule, to create, e.g., acrosslinked urethane/urea network, or both. As another example, inepoxy-based systems such as the second polymeric system discussed inmore detail below, a curing agent may simultaneously or sequentiallyfacilitate polymerization and network formation. In most other types ofpolymers, frequently formed through addition polymerization, curingagents serve only to crosslink polymers that have already been fully ordesirably polymerized. For the purposes of this disclosure, curingagents may also be referred to as either “chain extenders,”“crosslinkers,” or both.

As discussed above, however, the selection of the type of prepolymer andcuring agent determines the type of linkages present in the firstpolymeric system. For example, when a hydroxy-terminated curing is usedas a curing agent for a polyurea-based prepolymer, the resulting systemwill contain urethane linkages as a result of the excess isocyanatereacting with the hydroxy groups of the curing agent and is referred toas a polyurea-urethane system as opposed to a pure polyurea system,which contains only urea linkages. Similarly, a polyurethane prepolymercured with an amine-terminated curing agent will produce a systemincluding both urethane and urea linkages and is referred to as apolyurethane-urea system.

Suitable hydroxy-containing curing agents have a molecular weight ofabout 50 to about 4,000, and include, but are not limited to,unsaturated diols, such as:

-   -   1) 1,3-bis(2-hydroxyethoxy)benzene;        1,3-bis[2-(2-hydroxyethoxy)ethoxy]benzene;        1,3-bis{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy} benzene;    -   2) N,N-bis(β-hydroxypropyl)aniline;    -   3) hydroquinone-di(β-hydroxyethyl)ether;        resorcinol-di(β-hydroxyethyl)ether;    -   4) ethoxylates of the bis-phenols; bis(2-hydroxyethyl)        bisphenol; and    -   5) tetramethylxylylene diols; xylene glycol,        saturated diols, such as:    -   1) ethylene glycol; diethylene glycol; polyethylene glycol;        propylene glycol; dipropylene glycol; polypropylene glycol;        2-methyl-1,3-propanediol; 1,2-, 1,3-, 1,4-, or 2,3-butanediols;        2-methyl-1,4-butanediol; 2,3-dimethyl-2,3-butanediol;        1,5-pentanediol; neopentyl glycol; 1,6-hexanediol;        trimethylolpropane;    -   2) cyclohexyldimethylol;    -   3) 1,3-bis(2-hydroxyethoxy)cyclohexane;        1,3-bis[2-(2-hydroxyethoxy)ethoxy]cyclohexane;        1,3-bis{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane; and    -   4) PTMEG having a molecular weight of about 200 to about 4000,        unsaturated triols, such as castor oil (a.k.a. triricinoleoyl        glycerol), saturated triols, such as 1,2,4-butanetriol;        1,2,6-hexanetriol; trimethylolethane (a.k.a.        1,1,1-tri(hydroxymethyl)ethane); trimethylolpropane (a.k.a.        2,2-di(hydroxymethyl)-1-butanol); triethanolamine; and        triisopropanolamine, unsaturated tetraols, such as        2-propanol-1,1′-phenylaminobis and        2,4,6-tris(N-methyl-N-hydroxymethyl-aminomethyl)phenol,        saturated tetraols, such as pentaerythritol (a.k.a.        tetramethylolmethane); and tetrahydroxypropylene ethylenediamine        (a.k.a. N,N,N′,N′-tetrakis(2-hydroxypropyl)-ethylenediamine),        and other polyols such as mannitol (a.k.a.        1,2,3,4,5,6-hexanehexyl) and sorbitol (an enantiomer of        mannitol) (both saturated).

Suitable amine-containing curing agents may have a molecular weight ofabout 50 to about 5,000, and include, but are not limited to,unsaturated diamines, such as:

-   -   1) m-phenylenediamine; o-phenylenediamine; p-phenylenediamine;        2,4- and 2-6-toluene diamine; 1,2-, 1,3-, or        1,4-bis(sec-butylamino)benzene (Unilink 4100);        3,3′-dimethyl-4,4′-biphenylene diamine; 1,2-, 1,3-, or        1,4-bis(sec-butylamino) xylene;    -   2) 3,5-diethyl-(2,4- or 2,6-) toluenediamine;        3,5-dimethylthio-(2,4- or 2,6) toluenediamine;        3,5-diethylthio-(2,4- or 2,6-) toluenediamine;    -   3) 4,4′-diamino-diphenylmethane (a.k.a. 4,4′-methylene-dianiline        or “MDA”); 3,3′-dimethyl-4,4′-diamino-diphenylmethane;        3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-diphenylmethane (a.k.a.        4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine));        3,3′-dichloro-4,4′-diamino-diphenylmethane (a.k.a.        4,4′-methylene-bis(2-chloroaniline) or “MOCA”);        3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane;        3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (a.k.a.        4,4′-methylene-bis(2,6-diethylaniline) or “MDEA”);        2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane        (a.k.a. 4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or        “MCDEA”); 3,3′-dichloro-4,4′-diamino-diphenylmethane;        2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane (a.k.a.        4,4′-methylene-bis(2,3-dichloroaniline) or “MDCA”);        3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diaminodiphenylmethane;        4,4′-bis-(sec-butylamino)-diphenylmethane (Unilink 4200);        3,3′-dimethyl-4,4′-bis-(sec-butylamino)-diphenylmethane;        N,N′-dialkylamino-diphenylmethane;        3,3′,5,5′-tetraisopropyl-4,4′-diaminodiphenylmethane;        3,3′-dimethyl-5,5′-diisopropyl-4,4′-diaminodiphenylmethane;        3,3′-diethyl-5,5′-diisopropyl-4,4′-diaminodiphenylmethane;        3,3′-dimethyl-5,5′-di-t-butyl-4,4′-diaminodiphenylmethane;        isomers thereof;    -   4) trimethyleneglycol-di(p-aminobenzoate);        polyethyleneglycol-di(p-aminobenzoate);        polytetramethyleneglycol-di(p-aminobenzoate);    -   5) 2,3,5,6-tetramethyl-1,4-diaminobenzene; and    -   6) m-xylene diamine; m-tetramethylxylene diamine,        saturated diamines, such as:    -   1) ethylene diamine; 1,3-propylene diamine;        2-methyl-pentamethylene diamine; 1,3-pentanediamine;        hexamethylene diamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexane        diamine;    -   2) imino-bis(propylamine); methylimino-bis(propylamine) (a.k.a.        N-(3-aminopropyl)-N-methyl-1,3-propanediamine);        1,12-dodecanediamine;    -   3) 1,4-bis(3-aminopropoxy)butane (a.k.a.        3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine);        diethyleneglycol-bis(propylamine) (a.k.a.        diethyleneglycol-di(aminopropyl)ether);        4,7,10-trioxatridecane-1,13-diamine; polyoxyethylene diamines;        polyoxypropylene diamines; (ethylene oxide        capped)-polyoxypropylene ether diamines; polytetramethylene        ether diamines;    -   4) 1,4-diamino-cyclohexane; 1,3-diamino-cyclohexane;        1,2-diamino-cylcohexane; 1,4-diaminoethylcyclohexane;        1-methyl-3,5-diethyl-2,4 (2,6)-diaminocyclohexane;        1-methyl-3,5-dimethylthio-2,4 (2,6)-diaminocyclohexane;        1-methyl-2,6-diamino-cyclohexane; 1,2-, 1,3-, or        1,4-bis(methylamino)-cyclohexane; 1,2-, 1,3-, or        1,4-bis(sec-butylamino)-cyclohexane; 1,2-, 1,3-, or        1,4-bis(sec-butylamino methyl)-cyclohexane; isophorone diamine;    -   5) 4,4′-diamino-dicyclohexylmethane;        3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane;        3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane;        3,3′-dichloro-4,4′-diamino-dicyclohexylmethane;        3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane;        3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane (a.k.a.        4,4′-methylene-bis(2,6-diethylaminocyclohexane));        2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane;        3,3′-dichloro-4,4′-diamino-dicyclohexylmethane;        2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane;        3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-dicyclohexylmethane;        4,4′-bis(sec-butylamino)-dicyclohexylmethane (Clearlink® 1000);        N,N′-dialkylamino-dicyclohexylmethane;        3,3′-dimethyl-4,4′-bis(sec-butylamino)-dicyclohexylmethane        (Clearlink® 3000); N,N′-diisopropyl-isophorone diamine        (Jefflink® 754);        3-{[(5-amino-1,3,3-trimethylcyclohexyl)methyl]amino}-propanenitrile;        N,N′-diethylmaleate-2-methyl-pentamethylene diamine (Desmophen®        NH 1220); N,N′-di(ethylmaleate-amino)-dicyclohexylmethane        (Desmophen® NH 1420);        N,N′-di(ethylmaleate-amino)-dimethyl-dicyclohexylmethane        (Desmophen® 1520); polyamine/carbonyl adducts;    -   6) 1-methyl-3,5-dimethylthio-(2,4- or 2,6-)cyclohexyldiamine;        1-methyl-3,5-diethyl-(2,4- or 2,6-)cyclohexyldiamine;    -   7) N-aminoethylpiperazine; 1,2-, 1-3, 1,4-bis-(isocyanatomethyl)        cyclohexane;    -   8) 2,3,5,6-tetramethyl-1,4-diaminocyclohexane;    -   9) 3-bis-(1-amino-1-methylethyl)-cyclohexane (hydrogenated        version of m-TMXDA);        triamines, such as diethylene triamine; dipropylene triamine;        (propylene oxide)-based triamines (a.k.a. polyoxypropylene        triamines); trimethylolpropane-based triamines, glycerin-based        triamines, N-(2-aminoethyl)-1,3-propylenediamine (a.k.a.        N₃-amine) (all saturated), tetramines, such as triethylene        tetramine; N,N′-bis(3-aminopropyl)ethylenediamine (a.k.a.        N₄-amine) (both saturated), and other polyamines, such as        tetraethylene pentamine (also saturated).

Suitable amine-containing and hydroxy-containing hybrid curing agentsmay be monomeric, oligomeric, or polymeric, having at least one freereactive hydroxyl group and at least one free reactive amine group. Thehydroxyl and amine groups may be terminal or pendant groups on theoligomeric or polymeric backbone, and in the case of secondary aminegroups, may be embedded within the backbone. Non-limiting examples ofthe amine-containing and hydroxyl-containing hybrid curing agentsinclude monoethanolamine; monoisopropanolamine; diethanolamine; anddiisopropanolamine.

Saturated members of the above-listed curing agents are preferablychosen to react with saturated prepolymers, i.e., those formed fromsaturated isocyanates and saturated polyols or amine-terminatedpolymers, to form a saturated polyurethane or polyurea composition.Examples of saturated curatives include, but are not limited to,1,4-butanediol; ethylene glycol; diethylene glycol; polyethylene glycol;propylene glycol; dipropylene glycol; polypropylene glycol;2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol;2,3-dimethyl-2,3-butanediol; 1,4-cyclohexyldimethylol; 1,2-butanediol;1,3-butanediol; 1,4-butanediol; 2,3-butanediol; trimethylolpropane;cyclohexyldimethylol; triisopropanolamine; diethylene glycolbis-(aminopropyl)ether; 1,5-pentanediol; 1,6-hexanediol;1,3-bis-(2-hydroxyethoxy) cyclohexane; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]cyclohexane; 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane; polytetramethylene ether glycol havingmolecular weight ranging from about 250 to about 3900; ethylene diamine;hexamethylene diamine; 1-methyl-2,6-cyclohexyl diamine; 2,2,4- and2,4,4-trimethyl-1,6-hexanediamine;4,4′-bis-(sec-butylamino)-dicyclohexylmethane and derivatives thereof;1,4-bis-(sec-butylamino)-cyclohexane;1,2-bis-(sec-butylamino)-cyclohexane; 4,4′-dicyclohexylmethane diamine;1,4-cyclohexane-bis-(methylamine); 1,3-cyclohexane-bis-(methylamine);diethylene glycol bis-(aminopropyl)ether;2-methylpentamethylene-diamine; diaminocyclohexane; diethylene triamine;triethylene tetramine; tetraethylene pentamine; propylene diamine;dipropylene triamine; 1,3-diaminopropane; dimethylamino propylamine;diethylamino propylamine; imido-bis-(propylamine); monoethanolamine,diethanolamine; triethanolamine; monoisopropanolamine,diisopropanolamine; triisopropanolamine; isophoronediamine;N,N′-diisopropylisophorone diamine,3,3′-dimethyl-4,4′-bis(sec-butylamino)-dicyclohexylmethane, and mixturesthereof.

To further improve the shear resistance of the resulting elastomers, atrifunctional curing agent may also be used to help improvecross-linking. In such cases, a triol, such as trimethylolpropane, or atetraol, such as N,N,N′,N′-tetrakis (2-hydroxylpropyl) ethylenediamine,may be added to the curative blends. Useful triamine curing agents forimproving the crosslinking of polyurea elastomers include, but are notlimited to: propylene oxide-based triamines; trimethylolpropane-basedtriamines; glycerin-based triamines; N,N-bis{2-[(aminocarbonyl)amino]ethyl}-urea; N,N′,N″-tris(2-aminoethyl)-methanetriamine;N1-(5-aminopentyl)-1,2,6-hexanetriamine; 1,1,2-ethanetriamine;N,N′,N″-tris(3-aminopropyl)-methanetriamine;N1-(2-aminoethyl)-1,2,6-hexanetriamine;N1-(10-aminodecyl)-1,2,6-hexanetriamine; 1,9,18-octadecanetriamine;4,10,16,22-tetraazapentacosane-1,13,25-triamine;N1-{3-[[4-[(3-aminopropyl)amino]butyl]amino]propyl}-1,2,6-hexanetriamine;di-9-octadecenyl-(Z,Z)-1,2,3-propanetriamine; 1,4,8-octanetriamine;1,5,9-nonanetriamine; 1,9,10-octadecanetriamine; 1,4,7-heptanetriamine;1,5,10-decanetriamine; 1,8,17-heptadecanetriamine; 1,2,4-butanetriamine;propanetriamine; 1,3,5-pentanetriamine; N1-{3-[[4-[(3-aminopropyl)amino]butyl]amino]propyl}-1,2,6-hexanetriamine; N1-{4-[(3-aminopropyl)amino]butyl}-1,2,6-hexanetriamine; 2,5-dimethyl-1,4,7-heptanetriamine;N1-(6-aminohexyl)-1,2,6-hexanetriamine;6-ethyl-3,9-dimethyl-3,6,9-undecanetriamine; 1,5,11-undecanetriamine;1,6,11-undecanetriamine; N,N-bis(aminomethyl)-methanediamine;N,N-bis(2-aminoethyl)-1,3-propanediamine; methanetriamine;N1-(2-aminoethyl)-N2-(3-aminopropyl)-1,2,5-pentanetriamine;N1-(2-aminoethyl)-1,2,6-hexanetriamine;2,6,11-trimethyl-2,6,1-dodecanetriamine; 1,1,3-propanetriamine;6-(aminomethyl)-1,4,9-nonanetriamine; 1,2,6-hexanetriamine;N2-(2-aminoethyl)-1,1,2-ethanetriamine; 1,3,6-hexanetriamine;N,N-bis(2-aminoethyl)-1,2-ethanediamine;3-(aminomethyl)-1,2,4-butanetriamine; 1,1,1-ethanetriamine;N1,N1-bis(2-aminoethyl) 1,2-propanediamine; 1,2,3-propanetriamine;2-methyl-1,2,3-propanetriamine; and mixtures thereof.

In one embodiment, the curing agent is a blocked, delayed actioncurative that reacts slowly with the terminal isocyanate groups at roomtemperature. When the blocked, delayed action curative is heated to anelevated temperature, the curative rapidly cures the urethane or ureaelastomer. In this aspect of the invention, the blocked, delayed actioncurative can include a salt complex that deblocks at an elevatedtemperature. The deblocking temperature may be any suitable elevatedtemperature that results in freeing the curing agent. For example, thedeblocking temperature used to activate the curing process can be fromabout 175° F. to about 350° F., from about 185° F. to about 325° F.,from about 195° F. to about 315° F., or from about 205° F. to about 305°F.

One example of a suitable blocked, delayed action curative for use withthe first polymeric system is CAYTUR® 21, which is commerciallyavailable from Crompton Corporation of Middlebury, Conn. CAYTUR® 21 is ablocked, delayed action diamine curative that is used primarily withurethane elastomer prepolymers based on toluene diisocyanate andpolyether polyols. It consists of a complex of methylene dianiline (MDA)and sodium chloride dispersed in dioctyl phthalate, wherein the saltcomplex deblocks at a temperature ranging from 212° F. to 302° F.

In another embodiment, the curing agent is a modified curative blend asdisclosed in co-pending U.S. Patent Publication No. 2003/0212240, whichis incorporated by reference herein in its entirety. For example, thecuring agent of the invention may be modified with a freezing pointdepressing agent to create a curative blend with a slower onset ofsolidification and with storage stable pigment dispersion. The freezingpoint depressing agent is preferably added in an amount sufficient toreduce the freezing point of the curing agent by a suitable amount toprevent loss of pigment dispersion, but not affect the physicalproperties of the golf ball. Thus, a curative blend according to thepresent invention may include a polyamine adduct and a freezing pointdepressing agent.

The Second Polymeric System

The second system included in the IPN of the invention may be based onan epoxy or an acrylic resin. The epoxy-based system is cured with acuring agent/catalyzing agent, whereas the acrylic-based system requiresan initiator for polymerization. The particulars of each system arediscussed in more detail below, however, the second polymeric system iscured at the same time or substantially the same time as the firstpolymeric system in order to form the IPN.

The Epoxy System

Any cured epoxy resin is suitable for use as the second polymeric systemin the IPN of the present invention. Suitable epoxy resins include, butare not limited to, reaction products of bisphenol A andepichlorohydrin, reaction products of an aliphatic polyol andepichlorohydrin, and oxidized polyolefins. Examples of aliphatic polyolsinclude any of the saturated polyols discussed above with respect thefirst polymeric system. In one embodiment, the aliphatic polyol isglycerol. The oxidized polyolefins may be oxidized using any suitableacid, e.g., peracetic acid. In one embodiment, the epoxy resin is amodified epoxy resin including halogenated bisphenol. A commerciallyavailable bisphenol A epoxy resin is EPON®, a Jeffamine resinmanufactured by Huntsman Corporation of Austin, Tex.

In addition, epoxidized esters of unsaturated alcohols and unsaturatedcarboxylic acids are contemplated for use as the epoxy resin. In oneembodiment, the epoxy resin includes at least one of glycidyl glycidate;2,3-epoxybutyl-3,4-epoxypentanoate; 3,4-epoxy-3,4-epoxyhexyl;3,4-epoxypentanoate; or mixtures thereof. In another embodiment, thesecond polymeric system include epoxidized esters of unsaturatedmonohydric alcohols and polycarboxylic acids, such as diglycidyladipate; diglycidyl isophthalate; di(2,3-epoxybutyl) adipate;di(2,3-epoxybutyl) oxalate; di(2,3-epoxyhexyl) succinate;di(3,4-epoxybutyl) maleate; di(2,3-epoxyoctyl) pimelate;di(2,3-epoxybutyl) phthalate; di(2,3-epoxyoctyl) tetrahydrophthalate;di(4,5-epoxydodecyl) maleate; di(2,3-epoxybutyl) teraphthalate;di(2,3-epoxypentyl) thiodipropionate; di(5,6-epoxytetradecyl)diphenyldicarboxylate; di(3,4-epoxyheptyl) sulfonyldibutyrate;di(5,6-epoxypentadecyl) maleate; di(2,3-epoxybutyl) azelate;di(3,4-epoxybutyl) citrate; di(5,6-epoxyoctyl)cyclohexane-1,3-dicarboxylate; di(4,5-epoxyoctadecyl) malonate;tri(2,3-epoxybutyl)-1,2,4-butanetricarboxylate; and mixtures thereof.

Other examples of epoxy resins suitable for use with the presentinvention include, but are not limited to, epoxidized derivatives ofpolyethylenically unsaturated polycarboxylic acids; epoxidizedpolyesters that are the reaction product of an unsaturated polyhydricalcohol and/or an unsaturated polycarboxylic acid or anhydride groups;epoxidized polyethylenically unsaturated hydrocarbons; glycidyl ethersof novolac resins; and mixtures thereof.

The epoxy resin may be cured with a number of curing agents/catalyzingagents. In one embodiment, the curing agent is a Lewis base, such asalkali metal hydroxide. Lewis bases are those compounds containing anatom with an unshared electron pair in its outer orbital. They areattracted to areas of reduced electron density in the molecules withwhich they react. The organic bases, such as tertiary amines (R₃N:), arerepresentative of the more reactive-type Lewis bases suitable for curingepoxy resins.

In another embodiment, the curing agent is a Lewis acid, such as aphenol. In still another embodiment, the curing agent is an amine, suchas tri(dimethylaminomethyl-phenol and dimethylaminomethylphenol. In yetanother embodiment, the curing agent is an amide, such asamidopolyamine.

The curing agent for the epoxy system may also be an anhydride. Theanhydride may be alicylic, linear polymeric, aromatic, chlorinated,brominated, or mixtures thereof. Examples of suitable anhydrides to useas the curing agent include, but are not limited to, hexahydrophthalicanhydride, methyl hexahydrophthalic anhydride, dodecyl succinicanhydride, nadic methyl anhydride, and mixtures thereof. In oneembodiment, the anhydride is present in a blend or an adduct.

Those of ordinary skill in the art are familiar with the reactionmechanism of an epoxy resin and its curing agent. One example mechanism,using bisphenol A epoxy resin and a polyoxypropylene glycol based amine,is shown below:

The amines further react with the epoxy groups to build up the molecularweight of the epoxy system.

The amount of curing agent to epoxy resin is any suitable amount thatresults in a completely cured epoxy system. For example, the curingagent to epoxy resin ratio may range from about 0.4 to about 1.4 (on anequivalent basis). In one embodiment, the curing agent to epoxy resinratio is about 0.6 to about 1.2. In another embodiment, the ratio ofcuring agent to epoxy resin is about 0.6 to about 1.0.

The Acrylic Resin System

The IPN of the present invention may also be formed using a secondpolymeric system that is based on an acrylic resin. In particular, theacrylic resin system may be formed using an acrylate functional resinthat is polymerized with an initiator.

Although some polymeric systems may be formed throughself-polymerization, for example, such as polystyrene from styrenemonomer, when activated by heat or the appropriate energy, most chaingrowth polymerizations involve an initiator. The choice of initiator ofuse in the present invention depends on each polymer component to besynthesized, and any available initiator capable of polymerizing theselected monomers, oligomers, or pre-polymers are generally also presentin a precursor package. Suitable initiators can include, for example,free radical, cationic initiators, or ionic initiators. In cases wherecommercially available initiators contain inhibitors, the inhibitors maybe separated and removed from the initiator by known methods prior touse.

Suitable initiators for use with the acrylic resin system include, butare not limited to, benzoyl peroxide, t-amyl peroxide, and mixturesthereof.

Forming the IPN

The IPNs of the present invention include at least two precursorpackages, which correspond to the at least two polymeric systemsdescribed above. Each precursor package contains at least all thecompounds necessary to form one of the polymeric systems of the IPN.Compounds that may be used in a precursor package include any monomers,oligomers, or pre-polymers that are to be attached to the polymericsystem by polymerization.

For example, a precursor package for a first polymeric system mayinclude a blocked polyurethane or polyurea prepolymer, a chain extenderor curing agent, and, optionally, a “deblocking” agent. When referringto polymeric systems synthesized by step-growth polymerization, itshould be understood that monomers, oligomers, and pre-polymers refer toany or all compounds with functional groups that participate in thepolymerization and are attached to the resulting step-growth homopolymeror copolymer. A precursor package for the second polymeric system mayinclude an epoxy resin or acrylic resin and its respective curingagent/catalyzing agent/initiator.

Interpenetrating polymer networks according to the present invention maytypically be fabricated by a number of different methods known to one ofordinary skill in the art. Such fabrication processes include, but arenot limited to, the following groups of methods.

(1) At least two sets of pre-synthesized oligomeric or polymericcomponents are mixed together by any standard method or any method knownto one of ordinary skill in the art, such as, for example, melt mixing,solvating at least one component in a solution of at least one of theother components and a solvent or solvent mixture, or forming a solutionmixture from at least two solutions, each containing at least one set ofcomponents and a solvent or solvent mixture. In cases where solventmixing is involved, e.g., a coating composition including an IPN of thepresent invention, the majority of the solvent or solvent mixture shouldbe removed after mixing, for example, by evaporation, boiling,precipitation of the non-solvent components, or the like, preferablysuch that the IPN contains less than 10 percent solvent, or morepreferably is substantially free of solvent. The mixing process shouldallow for sufficiently intimate mixing of the components, for example,such that the at least two components are at least partiallyco-entangled. At least one of the at least two intimately mixedcomponents can then be crosslinked. If both components are to becrosslinked, the crosslinking can occur simultaneously or sequentially.

(2) At least one non-polymerized precursor package can be incorporatedinto at least one other pre-synthesized oligomeric or polymericcomponent, which may or may not already be a crosslinked network, whichincorporation can occur by any method that facilitates intimate mixingof the at least one precursor package with the at least onepre-synthesized component, for example, such as by swelling the at leastone pre-synthesized component with the at least one precursor package,optionally under an applied pressure. Once the components are intimatelymixed, the at least one precursor package can then be appropriatelypolymerized. In the event that the at least one pre-synthesizedcomponent is/are already crosslinked and a semi-IPN is desired, afurther crosslinking reaction may not be necessary. Otherwise, at leastone component of the at least one precursor package, now polymerized,may be crosslinked. Alternately, at least one component of the at leastone precursor package may be crosslinked and polymerized simultaneously.If the at least one pre-synthesized component is/are not alreadycrosslinked, then the at least one pre-synthesized component and the atleast one polymerized precursor package component may be crosslinkedsimultaneously or sequentially. Alternately, if the at least onepre-synthesized component is/are not already crosslinked and a semi-IPNis desired, at least one of either set of components can be crosslinked.

(3) The at least two precursor packages can be mixed together by anymethod that facilitates intimate mixing of the compounds in the at leasttwo precursor packages. The at least two intimately mixed precursorpackages can then be polymerized and/or crosslinked in any order to forman IPN of the present invention. In one embodiment, the at least twoprecursor packages can be polymerized simultaneously or sequentially,but not crosslinked, yielding an intimately mixed blend of the at leasttwo polymerized precursor package components. Then, one or more of thepolymerized components can be crosslinked by an appropriate crosslinkingmethod, and, if more than one of the polymerized components are to becrosslinked, the crosslinking can be done simultaneously orsequentially. Alternately, for one or more of the polymerizedcomponents, the crosslinking reaction may occur simultaneously with thepolymerization reaction. In another embodiment, at least one of the atleast two intimately mixed precursor packages can be polymerized andcrosslinked in the presence of the other precursor package(s), afterwhich the subsequent steps are similar to method #2 (after the initialintimate mixing).

It should be understood that certain rapid-forming IPN systems may needto be prepared using a quick-forming process, such as reaction injectionmolding (RIM), which is a processing method known for use in formingarticles or materials out of rapidly curing polymer systems. Thus, thefaster the formation of a given IPN system, the more suitable the use ofRIM to process it. Indeed, if the IPN gelation time is less than about60 seconds, preferably less than about 30 seconds, RIM is preferred overother conventional processing techniques. In the RIM process, at leasttwo or more reactive, low-viscosity, liquid components are generallymixed, for example, by impingement, and injected under high pressure(e.g., at or above about 1200 psi) into a mold. The reaction times forRIM systems are much faster than in conventional lower-pressure mixingand metering equipment. The precursor packages used for the RIM process,therefore, are typically much lower in viscosity to better facilitateintimate mixing in a very short time.

(4) Each of the at least two precursor packages can be at leastpartially polymerized separately, and preferably simultaneously, atwhich point the at least partially polymerized precursor packages can bemixed together in a manner sufficient to result in intimate mixing ofthe components of the at least two, at-least-partially-polymerizedcomponents. In some urethane-epoxy systems, the total gelation time mayrange from about 40 to 100 seconds. The remainder of the polymerizationsof the intimately mixed components then occur simultaneously, althoughone polymerization may be sufficiently complete before any other. Then,after all polymerizations are sufficiently complete, one or more of thepolymerized components can be crosslinked by an appropriate crosslinkingmethod, and, if more than one of the polymerized components are to becrosslinked, the crosslinking can be done simultaneously orsequentially. Alternately, for one or more of the polymerizedcomponents, the crosslinking reaction may occur simultaneously with thepolymerization reaction.

In one embodiment, the precursor packages are mixed separately until asufficient viscosity is attained, preferably from about 2,000 cPs to35,000 cPs, more preferably from about 8,000 cPs to 30,000 cPs, mostpreferably from about 15,000 cPs to 26,000 cPs.

When forming an IPN including an epoxy resin system, any of the methodsabove can be used. Generally, the blocked polyurea or polyurethaneprepolymer is mixed with its respective curing agent, e.g., a shortchain diol or diamine, the epoxy resin, and the epoxy curingagent/catalyzing agent. The addition of heat, or a “deblocking” agent,is used to deblock the isocyanate groups, which react with the curingagent, and form urethane linkages or urea linkages depending on the typeof curing agent used. The epoxy system simultaneously or sequentiallyreacts with its curing agent/catalyzing agent to form a cured epoxysystem. In one embodiment, the IPN includes at least about 50 percent byweight of the polyurethane system, preferably about 80 percent orgreater, more preferably about 90 percent or greater

In the case where at least one of the polymeric systems is a thermosetmaterial, the mixture of the two systems can be made in a number ofways, such as by grinding a cured epoxy polymer into a powder; mixingthe proper proportion of the powdered epoxy polymer with thepolyurethane or polyurea prepolymer to uniformly disperse the epoxypowder, but before polymerization, gelation, or solidification occurs;and shaping the mixture into a golf equipment component (e.g., a golfall or portion thereof).

When forming an IPN of the invention that includes an acrylic resin, theblocked polyurethane or polyurea prepolymer is mixed with its respectivecuring agent, e.g., a short chain diol or diamine, an acrylate resin,and an initiator. As with the epoxy-based IPN, once the temperature ishigh enough to deblock the isocyanate groups in the prepolymer, urethaneor urea linkages form (depending on the curing agent selected) to formthe first system while the acrylate polymerization is initiated to formthe second system. In the alternative, a “deblocking” agent may be usedinstead of, or in combination with, raising the temperature to deblockthe isocyanate groups in the prepolymer. Once the isocyanate groups aredeblocked, however, the IPN forms as the first and second polymericsystems cure simultaneously or sequentially. In one embodiment, an IPNaccording to the invention may include an acrylate homopolymer orcopolymer or a homopolymer or copolymer containing a conjugated diene,especially polybutadiene, but may not include both.

If heat is used to deblock the isocyanate groups, the temperaturerequired to expose the isocyanate groups is dependent on the type ofblocking agent. A catalyst may be used to lower the deblockingtemperature. Suitable catalysts include, but are not limited to,organometallic compounds, tertiary amines, quaternary ammonium salts,and combinations thereof. For example, dibutyltin dilaurate, dibutyltindiacetate, zinc naphthenate, lead naphthenate, bismuth salts, titanates,Co, Mg, Sr, and Ba salts of hexanoic, octanoic, naphthenic, andlinolenic acids, metal acetylacetonates, and mixtures thereof arecontemplated as catalysts for the deblocking mechanism. In oneembodiment, a combination of organotin compounds and quaternary ammoniumsalts are used for catalysis to lower the deblocking temperature.

Crosslinking agents for each of the polymeric systems may be included inthe precursor package to be mixed in with the systems initially,especially if they need to be externally activated, or may be addedsubsequent to the intimate mixing step, especially to avoid prematurecrosslinking by heating or exposure to activating energy or compounds.If activation is needed for crosslinking one or more of the at least twointimately mixed components, it is typically performed after an intimatemixing step. Activators for crosslinking may affect an agent or a partof the component itself, for example, such as a carbon-carbon doublebond or a labile carbon-hydrogen bond, and generally include, but arenot limited to, heat, light, UV radiation, x-rays, microwave radiation,and gamma radiation.

It should be understood that each method of crosslinking should bechosen to match up with the choice of starting materials andpolymerization scheme used to synthesize each polymer system. It shouldalso be noted that each method of crosslinking should typically notsignificantly degrade or be counterproductive toward polymerization ornetwork formation of other components in the IPNs of the presentinvention.

A number of suitable polymerization and/or crosslinking techniques arecontemplated to polymerize or crosslink the polymeric systems of theIPN. As used herein, the phrase “polymerization and/or crosslinkingtechniques” refers to the optional use of one or more initiators inconjunction with the chosen radiation cure technique or techniques.Thus, in one embodiment, the formation of an IPN of the presentinvention includes polymerizing and/or crosslinking one or morepolymers, prepolymers, oligomers and/or monomers sequentially orsimultaneously using one or more polymerization and/or crosslinkingtechniques. In particular, the formation of an IPN includes sequentiallyor simultaneously exposing one or more polymers, prepolymers, oligomersand/or monomers to:

-   -   1) an energy source selected from the group consisting of        thermal/heat (i.e., microwave or infrared), UV radiation,        visible radiation, electron beam radiation, x-ray radiation,        gamma radiation, and combinations thereof, in the presence of an        initiator; and    -   2) optionally one or more additional energy sources selected        from the group consisting of thermal/heat (i.e., microwave or        infrared), UV radiation, visible radiation, electron beam        radiation, x-ray radiation, gamma radiation, and combinations        thereof, in the presence of an initiator.        The initiator is optional and can be present or absent when        electron beam radiation, x-ray radiation, thermal radiation, or        gamma radiation is utilized in forming an IPN.

The energy source is selected such that its exposure to one or morepolymers, prepolymers, oligomers and/or monomers does not adversely ordetrimentally affect crosslinking and/or polymerization reactions or thecharacteristics of the final crosslinked and/or polymerized IPN. Forexample, an IPN including polyurea and acrylate requires low temperaturefor a fast cure of polyurea prepolymer, but curing the acrylate systemgenerally requires heat, which adversely affects the curing of thepolyurea by reducing the reaction rate and cosmetically changing curedpolyurea. Electron beam radiation may be chosen to cure the acrylatebecause it can be utilized while avoiding the adverse or detrimentaleffects caused heat.

In one embodiment, the one or more additional energy source is electronbeam radiation. In particular, the formation of an IPN includessequentially or simultaneously exposing one or more polymers,prepolymers, oligomers and/or monomers to:

-   -   1) an energy source selected from the group consisting of        thermal radiation/heat, UV radiation, visible radiation,        electron beam radiation, x-ray radiation, gamma radiation, and        combinations thereof; and    -   2) electron beam radiation.        The use of a low power electron beam source allows more        efficient dosage of electrons and also helps prevent unwanted        reactions with the final crosslinked/polymerized IPN.

The electron beam tube is a vacuum tube having a base end and a windowend. An extended filament is disposed within the beam tube proximate tothe base end. The filament generates electrons in conjunction withelectron beam forming electrodes. The electrons from the filament (i.e.,electron beam source) are directed toward and through the beam window ofthe electron beam tube. A low power electron beam tube is preferred. Thebeam energy from a low power beam tube is below about 125 kV(kilovolts), typically between about 15-80 kV (or any valuetherebetween), more typically between about 20-75 kV and most typicallybetween about 30-65 kV. The voltage to the power supply (input voltagefrom about 10 to about 1,000 volts) is preferably about 110 volts (orless) and its operating power is preferably about 100 watts (or less).However, the output voltage of the beam tube may be between 20-100 kV orany value therebetween. Likewise, the operating power of the electronbeam may be from about 10-1,000 watts or any value therebetween.

The amount of time required for the systems to cure is variable,depending on the type of constituents in the two polymeric systems, thethickness of the material, the cure temperature, and other factors knownto those of skill in the art. In one embodiment, the cure time is about5 seconds to about 1 hour. In another embodiment, the cure time is about15 seconds to about 45 minutes, preferably about 30 seconds to about 30minutes. Alternatively, the cure time can be 1 hour or more. Forexample, the IPNs of the invention may be cured overnight at roomtemperature.

In addition, the amount of radiation energy needed to sufficientlyinitiate polymerization, cure, and/or crosslink the composition dependsupon a number of factors including, for example, the chemical identityof the composition and precursors, as well as the initiator, radiationsource chosen, and length of exposure time of the polymer components tothe energy source. As discussed above, thermal radiative sources includeinfrared and microwave sources. Conditions for thermal or heat initiatedpolymerizations typically are from about 35° C. to about 300° C.,preferably from about 50° C. to about 200° C. and for a time of aboutfractions of minutes to about thousands of minutes. Examples of thermalfree radical initiators include azo compounds, peroxides, persulfates(e.g., potassium persulfate, sodium persulfate, and ammoniumpersulfate), and redox initiators.

If actinic radiation is utilized, such as ultraviolet or visible light,a photoinitiator may be utilized. Upon being exposed to ultraviolet orvisible light, the photoinitiator generates a free radical source or acationic source. This free radical source or cationic source theninitiates the polymerization. In free radical processes, however, aninitiator is optional when a source of electron beam radiation, x-ray orgamma radiation energy is utilized. Thus, an initiator may be present orabsent when the energy source is electron beam radiation, x-ray or gammaradiation energy. Gamma radiation and electron beam radiation are usefulbecause of their excellent penetration at ambient temperature allowsmore control in the quiescent conditions. Gamma radiation and electronbeam radiation are also advantageous because they require minimalcooling of the cured inks (the curing is done at ambient or roomtemperature), the ink are almost instantaneously cured, obviate orreduce the need for costly ventilating systems, and, in the case of lowpower electron beam radiation, require low energy to cure. Additionally,curing by gamma radiation or electron beam radiation allows thecombination of several ink compositions in the same curing cycle, whichmay not be possible for thermal curing because the different inkcompositions may require different temperatures or cure times.

Suitable photoinitiators include, for example, those that absorb in thewavelength range from about 0.001 nm to 700 nm, preferably from about100 nm to about 650 nm, more preferably from about 190 nm to about 600nm. Photoinitiators include peroxides, azo compounds, quinines (e.g.,substituted and unsubstituted anthraquinones, camphor quinone,alkyl-camphorquinone), benzophenones (e.g., 4-methylbenzophenone,benzophenone, 4,4′-bisdimethylamine-benzophenone, 1-hydroxycyclohexylphenyl ketone), nitroso compounds, acyl halides, hydrazones, mercaptocompounds, pyrylium compounds, triacylimidazoles, organophosphoruscompounds (e.g., acylphosphine oxides,2,4,6-trimethylbenzoyldiphenylphosphine oxide), bisimidazoles,chloroalkyltriazines, benzoates (e.g., ethyl 4-(dimethylamino)benzoate),benzoyl compounds (e.g., acrylic or methacrylic[(2-alkoxy-2-phenyl-2-benzoyl)ethyl]esters, 4-benzoyl-4′-methyldiphenylsulfide, 1-benzoylcyclohexanol), benzoin ethers (e.g., substituted andunsubstituted C₁-C₈ alkyl benzoin ethers, such as benzoisobutyl ether),benzil ketals (e.g., benzyldimethyl ketal), thioxanthones (e.g.,2-isopropylthioxanthone and 4-isopropylthioxanthone), acetophenonederivatives (e.g., 2,2-dimethoxy-2-phenyl-acetophenone,2,2-diethoxyacetophenone, 2,2-diacetoxyacetophenone, chlorinatedacetophenone, hydroxyacetophenone), ketones (e.g.,2-methyl-1-(4-[methylthio]phenyl)-2-(4-morpholinyl)-1-propanone,2-hydroxy-2-methyl-1-phenylpropan-1-one, 4-(2-hydroxyethoxy)phenyl2-hydroxy-2-propyl ketone,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)furan-1-one),metallocenes (e.g., Group VIII metallocenes, perfluorinateddiphenyltitanocenes), hexafluorophosphate salts (e.g.,(η⁵-cyclopentadienyl)(η⁶-isopropylphenyl)iron(II) hexafluorophosphate,triphenylsulfonium hexafluorophosphate), sulfonium salts, diacrylates(e.g., butanediol diacrylate, dipropylene glycol diacrylate, hexanedioldiacrylate, 4-(1,1-dimethylethyl)cyclohexyl acrylate, trimethylolpropanetriacrylate and tripropylene glycol diacrylate), polyols (e.g.,polyethylene glycol), pyrollidones (e.g., N-vinyl pyrollidone) andmixtures thereof.

Examples of commercially available photoinitiators include, but are notlimited to, Vicure 10, 30 (made by Stauffer Chemical), Irgacure 184,651, 2959, 907, 369, 1700, 1800, 1850, 819 (made by Chiba SpecialtyChemicals), Darocurel 173 (made by EM Chemical), Quantacure CTX, ITX(made by Aceto Chemical), Lucirin TPO (made by BASF). Other examples ofsuitable photoinitiators are described in, for example, U.S. Pat. No.6,500,495, the entirety of which is incorporated herein by reference.

Cationic initiators include Group IA or Group IIA organo compounds, arylsulfonium salts, hexafluorometallic salts, Bronsted acids, Lewis acidsor mixtures thereof. In particular, cationic initiators includesec-butyllithium, n-butyllithium, other (C₁-C₁₀)alkyllithiums,aryllithiums, sulfonic acids (e.g. sulfuric acid), phosphoric acid,perchloric acid, triflic acid, BF₃, aluminum halides (e.g., AlCl₃,AlBr₃), triarylsulfonium salts, diaryliudonium salts or mixturesthereof.

Peroxide and organic peroxide initiators typically are R—O—O—R₁, whereinR and R₁ are each independently selected from the group consisting ofhydrogen, (C₁-C₂₀)alkyl, (C₁-C₂₀)alkylene, (C₁-C₂₀)alkylyne,(C₁-C₂₀)cycloalkyl, and substituted or unsubstituted (C₆-C₂₄)aryl,wherein aryl may be phenyl, naphthyl, biphenyl, thienyl or pyridyl andthe aryl moiety may in each case be mono- to trisubstituted by F, Cl,Br, I, OH, CF₃, NO₂, CN, OCF₃, O—(C₁-C₁₀)alkyl, NH₂, NH(C₁-C₆)alkyl,COOH, COO(C₁-C₆)alkyl. As used herein, “substituted” refers toadditional moieties or groups that are attached to and found in R andR₁, which includes, but are not limited to F, Cl, Br, I, OH, CF₃, NO₂,CN, OCF₃, O—(C₁-C₁₀)alkyl, NH₂, NH(C₁-C₆)alkyl, COOH, COO(C₁-C₁₀)alkyl,(C₁-C₁₀)alkyl, (C₂-C₁₀)alkenyl, (C₂-C₁₀)alkynyl, (C₁-C₁₀)alkyl-COOH,(C₁-C₁₀)alkyl-aryl, wherein aryl may be phenyl, naphthyl, biphenyl,thienyl or pyridyl and the aryl moiety may in each case be mono-, di- ortri-substituted by F, Cl, Br, I, OH, CF₃, NO₂, CN, OCF₃,O—(C₁-C₁₀)alkyl, NH₂, NH(C₁-C₆)alkyl, COOH, COO(C₁-C₆)alkyl.

Examples of peroxide and organic peroxide initiators include, but arenot limited to, di(2-tert-butyl-peroxyisopropyl)benzene peroxide orbis(tert-butylperoxy)diisopropylbenzene,2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide,di-tert-butyl peroxide, di-tert-amyl peroxide, benzoyl-5-peroxide,tert-butyl hydroperoxide, benzoyl peroxide, acetyl peroxide, decanoylperoxide, dicetyl peroxydicarbonate, di(4-tert-butylcyclohexyl)peroxydicarbonate (available under the trade designation PERKADOX 16,from Akzo Chemicals, Inc., Chicago, Ill.), di(2-ethylhexyl)peroxydicarbonate, tert-butylperoxypivalate (available under the tradedesignation LUPERSOL 11, from Lucidol Division, Atochem North America,Buffalo, N.Y.) and tert-butylperoxy-2-ethylhexanoate (available underthe trade designation TRIGONOX 21-C50, from Akzo Chemicals, Inc.,Chicago, Ill.).

Azo compounds include, but are not limited to,4,4′-azobis(isobutyronitrile), 4,4′-azobis(cyanovalerate),4,4′-azobis(cyanovaleric acid),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (available under thetrade designation VAZO 33); 2,2′-azobis(2-amidinopropane)dihydrochloride (available under the trade designation VAZO 50);2,2′-azobis(2,4-dimethylvaleronitrile) (available under the tradedesignation VAZO 52); 2,2′-azobis(isobutyronitrile) (also known as AIBN,available under the trade designation VAZO 64);2,2′-azobis-2-methylbutyronitrile (available under the trade designationVAZO 67); 1,1′-azobis(1-cyclohexanecarbonitrile) (available under thetrade designation VAZO 88), all of which are available from E.I. Dupontde Nemours and Company, Wilmington, Del., and2,2′-azobis(methylisobutyrate) (available under the trade designationV-601 from Wako Pure Chemical Industries, Ltd., Osaka, Japan), and otherazo compounds.

In one embodiment, the free radical initiator is an inhibitor-containingperoxide, such as 2,6-di-tert-butylbenzoquinone,2,6-di-tert-butyl-4-methylene-2,5-cyclohexadiene-1-one,2,6-di-tert-butyl-4-hydroxybenzaldehyde,2,6-di-tert-butyl-4-isopropylphenol, 4,4′-methylenebis-(2,6-di-tert-butylphenol),1,2-bis-(3,5-di-tert-butyl-4-hydroxyphenyl)ethane,2,3,5,6-tetramethylbenzoquinone, 2-tert-butylhydroquinone,2,2′-methylenebis-(4-methyl-6-tert-butylphenol), and the like, andmixtures thereof. The initiator, i.e., photoinitiator, free-radicalinitiator or cationic initiator, is generally present in an amountsufficient to initiate a polymerization resulting in a polymer having anumber average molecular weight suitable for use in golf balls, which istypically from about 1,000 to about 10,000,000 grams/mole.Alternatively, the initiator (i.e., photoinitiator, free radicalinitiator or cationic initiator) may be present in an amount greaterthan about 0.01 parts per hundred of the polymer component, preferablyfrom about 0.01 to about 15 parts per hundred of the polymer component,and more preferably from about 0.1 to about 10 parts per hundred of thepolymer component, and most preferably from about 0.2 to about 5 partsper hundred of the total polymer component. It should be furtherunderstood that heat often facilitates initiation of the generation offree radicals in the aforementioned compounds.

In another embodiment, the initiator is selected to suit or match theradiation cure technique that is used to initiate the polymerizationprocess. For example, a photoinitiator is used when ultraviolet (“UV”)curing is the radiation cure technique. In another example, a thermalfree radical initiator is used when thermal or heat curing is theradiation cure technique. It is possible to use a photoinitiator inthermal or heat curing, or a thermal free radical initiator in UVcuring. Thus, the present invention encompasses the use of any initiatorin conjunction with any radiation cure technique so long as theinitiator that is chosen initiates the polymerization process.

In one embodiment, the free-radical source may alternatively oradditionally be one or more of an electron beam, visible light, UV orgamma radiation, x-rays, or any other high-energy radiation sourcecapable of generating free radicals. Thus in one example, an initiatormay or may not be utilized when gamma radiation, x-ray, or electron beamradiation is the radiation cure technique. Such initiators form freeradicals and/or cations that initiate polymerization upon exposure togamma radiation, x-ray or electron beam radiation.

IPN as a Coating Composition

As briefly addressed above, the IPNs of the present invention may alsobe used as a coating. The method of forming the IPN when it is intendedto be used as a coating is similar to that described above, however, themixture of components is prepared in a solution with a solvent such asmethyl isobutyl ketone, toluene, and the like. The solvent may be usedin an amount of about 0.05 to about 4 pounds solvent per pound of resin.In one embodiment, the solvent to resin ratio is about 0.08 to about 3by pound weight. In another embodiment, the solvent to resin ratio isabout 1 pound to about 2.5 by pound weight. The ratio of the firstpolymeric system, i.e., the polyurethane or polyurea prepolymer, to thesecond polymeric system, i.e., the epoxy resin or acrylate resin, ispreferably about 0.1 to about 1.0 by weight. In one embodiment, theratio of the prepolymer to epoxy resin or acrylate resin is about 0.2 toabout 0.8 by weight. In another embodiment, the prepolymer to epoxy oracrylate resin ratio is about 0.3 to about 0.7 by weight.

The solution is applied to the surface of the golf equipment, e.g., anoutermost cover of a golf ball, a golf club head, a golf shoe, a golfbag, by any suitable method. For example, dipping, spraying, andbrushing are application methods contemplated by the present invention.Once applied, the solution is cured in a manner similar to the onediscussed above. For example, the coated surface may be exposed to anelevated temperature to deblock the isocyanate groups in thepolyurethane or polyurea prepolymer. The elevated temperature will alsoactivate the epoxy or acrylate resin reaction so that the second systemwill cure simultaneously with the polyurethane or polyurea system toform the IPN of the present invention. As mentioned above, thetemperature required for deblocking the isocyanate groups and initiatingthe epoxy or acrylate resin reaction is a function of the type ofblocking agent, the type and amount of curing agents/catalyzingagents/initiators, as well as other factors known to those of skill inthe art.

Furthermore, as discussed above, a catalyst may be added to the solutionbefore it is applied to decrease the temperature and/or time required todeblock the isocyanate groups.

As those of ordinary skill in the art are aware, the cure time is highlydependent on the temperature and constituents of the composition. Forexample, the cure time for an IPN coating composition of the presentinvention can be from about 5 seconds to 24 hours, from about 5 secondsto about 1 hour, from about 5 seconds to about 30 minutes, from about 5seconds to about 15 minutes, from about 5 seconds to about 5 minutes,from about 5 seconds to about 2 minutes, or from about 5 seconds toabout 30 seconds.

Additives

Other compounds useful in polymerization of the individual polymericsystems of the IPNs of the present invention may also be added to aprecursor package as the situation warrants providing that the compoundsare not significantly counterproductive toward polymerization or networkformation of other components in the IPNs of the present invention. Suchcompounds should generally be chosen based on the specifics of thestarting materials, polymerization scheme, and crosslinking reactionused to synthesize each polymer component or network.

For example, accelerators or catalysts may be included in a precursorpackage to control the speed and/or duration of polymerization and/orcrosslinking reaction(s), if a particular component is crosslinked. Anyaccelerator or catalyst known to one of ordinary skill in the art or anystandard accelerator or catalyst may be used in a precursor package inthe present invention. It should be understood, however, that theaccelerator or catalyst used in a given precursor package should bechosen based on the specifics of the starting materials, polymerizationscheme, and crosslinking reaction, used to synthesize each polymercomponent or network. For example, the catalyst may be the same ordifferent from the catalyst used to decrease the temperature required todeblock the isocyanate groups in the first polymeric system.

Suitable catalysts include, but are not limited to, Lewis acids, forexample, such as halides of boron, aluminum, indium, tin, antimony, anytransition metal, particularly vanadium, zinc, zirconium, indium,manganese, molybdenum, cobalt, titanium, or tungsten, or mixturesthereof. Exemplary catalysts include chlorides and fluorides of boron,aluminum, or titanium, or mixtures thereof, and more preferably includeboron trifluoride, aluminum trichloride, titanium (III) or (IV)chloride, or mixtures thereof. Other suitable catalysts include, but arenot limited to, Lewis bases, inorganic bases, primary and secondaryamines, and amides. Other catalysts include, but are not limited to,oxides, such as magnesium oxide, or aluminum oxide; tertiary amines,such as N,N-dimethylaminopyridine, or benzyldimethylamine; imidazoles,such as 2-ethyl-4-methylimidazole; and phosphines, such astriphenylphosphine, or tributylphosphine. Catalysts may also includemixtures of any of these listed compounds with one or more othercomponents.

Suitable accelerators include, but are not limited to, sulfonamides,such as benzenesulfonamide; ureas, such as3-(p-chlorophenyl)-1,1-dimethylurea, or3-(3,4-dichlorophenyl)-1,1-dimethylurea; and acids, such as phthalicacid, benzoic acid, or p-toluenesulfonic acid. In one embodiment, acarboxylic acid compound may be used as an accelerator, particularlywhen the first polymeric system is polyurethane-based.

Optionally, additional curing agents may also be added to a precursorpackage to facilitate the curing of a particular polymeric system.Suitable chain extenders may vary depending on the polymers or networksincluded in the IPN, but, for step-growth or condensation polymers orepoxies, suitable curing agents generally include polyols, including,for example, telechelic diols, telechelic alkanediols, such as ethyleneglycol, 1,4-butanediol, 1,6-hexanediol, and the like, or mixturesthereof; a polyamine, including, for example, telechelic diamines,telechelic alkanediamines, such as ethylenediamine, propylenediamine,and the like, or mixtures thereof; a cyclic polyol or polyamine, forexample, such as diaminocyclohexane; or mixtures thereof. Suitablecrosslinkers may also vary depending or networks included in the IPN,and include, but are not limited to any chain extender; a disulfide orpolysulfide; a diisocyanate or polyisocyanate; excess diisocyanate orpolyisocyanate; compounds containing or able to generate or activate afree radical; a form of energy able to generate or activate afree-radical, for example, such as heat, visible light, ultravioletlight, x-rays, γ-rays, other energy or radiation, or a mixture thereof;divalent or multivalent salts; or a mixture thereof.

Other curing agents may be reactive upon addition to a precursor packageor to a polymer component or may require activation of some sort tobegin curing. Certain IPN precursors, prepolymers, or polymers, when theproper activators or initiators are used, as understood by those ofordinary skill in the art, can undergo self-polymerization, to formhigher molecular weight polymers, or self-crosslinking, to form anetwork structure, or both. These self-reactions advantageously may befacilitated by one or more catalysts.

Certain curing agents may already be present in a precursor package asthey may derive from a functional group or active site on a polymercomponent. Other curing agents may also be comonomers, for example, suchas multifunctional compounds in step-growth polymerization reactions,such as polyamines, polyisocyanates, polyols, or the like, or mixturesthereof, or compounds containing two sites across which an additionpolymerization may proceed, such as conjugated dienes, non-conjugateddienes, divinyl compounds, conjugated or non-conjugated cycliccompounds, divalent or multivalent salts, or mixtures thereof. One ofordinary skill in the art should be able to determine for a particularIPN system whether certain curing agents function as chain extenders,crosslinkers, or both. It should be understood that any curing agentsalready present in a precursor package or useful in another capacity inthe polymer component of the IPN system shall not be consideredadditional curing agents for that polymer component.

Fillers may also be used in the IPNs of the present invention. Fillerstypically include processing aids or compounds to affect rheological andmixing properties, the specific gravity (i.e., density-modifyingfillers), the modulus, the tear strength, reinforcement, and the like. Adensity adjusting filler may be used to control the moment of inertia,and thus the initial spin rate of the ball and spin decay. Fillers aretypically polymeric or inorganic in nature, and, when used, aretypically present in an amount from about 0.1 to 50 weight percent ofthe layer in which they are included. Any suitable filler available toone of ordinary skill in the art may be used. Exemplary fillers include,but are not limited to, precipitated hydrated silica; clay; talc; glassfibers; aramid fibers; mica; calcium metasilicate; barium sulfate; zincsulfide; lithopone; silicates; silicon carbide; diatomaceous earth;polyvinyl chloride; carbonates such as calcium carbonate and magnesiumcarbonate; metals such as titanium, tungsten, aluminum, bismuth, nickel,molybdenum, iron, copper, boron, cobalt, beryllium, zinc, and tin; metalalloys such as steel, brass, bronze, boron carbide whiskers, andtungsten carbide whiskers; metal oxides such as zinc oxide, iron oxide,aluminum oxide, titanium oxide, magnesium oxide, and zirconium oxide;particulate carbonaceous materials such as graphite, carbon black,cotton flock, natural bitumen, cellulose flock, and leather fiber; microballoons such as glass and ceramic; fly ash; cured, ground rubber; orcombinations thereof.

Various foaming agents or blowing agents may also be used in the IPNs ofthe present invention. Foamed polymer blends may be formed by blendingceramic or glass microspheres with polymer material. Polymeric, ceramic,metal, and glass microspheres may be solid or hollow, and filled orunfilled.

Additional materials conventionally included in golf ball compositionsmay also be included in the IPNs of the present invention. Theseadditional materials include, but are not limited to, coloring agents,reaction enhancers, whitening agents, UV absorbers, hindered amine lightstabilizers, defoaming agents, processing aids, and other conventionaladditives. Stabilizers, softening agents, plasticizers, includinginternal and external plasticizers, impact modifiers, foaming agents,excipients, reinforcing materials and compatibilizers can also be addedto any composition of the invention. All of these materials, which arewell known in the art, are added for their usual purpose in typicalamounts.

IPN Properties

Compatibility of the IPNs of the present invention can be evidenced bycomparing experimentally measured properties, such as the relative glasstransition temperatures (or the difference between them, denoted asΔT_(g)) or the relative crystallinity or crystalline perfection (asrepresented by the area under the melting endotherm), if at least onecomponent of the IPN is crystallizable. These properties may beexperimentally observed by a number of different instruments, such as adifferential scanning calorimeter (“DSC”) or dynamic mechanical analyzer(“DMA”) or dynamic mechanical thermal analyzer (“DMTA”).

Preferably, the formation of an IPN reduces the ΔT_(g) between at leasttwo of the polymeric components of the IPN at least about 5 percent ascompared with the ΔT_(g) between a polymer blend containing the same twopolymeric components. In one embodiment, the formation of an IPN reducesthe ΔT_(g) between at least two of the polymeric components of the IPNat least about 10 percent over that of a polymer blend containing thesame two polymeric components. In another embodiment, the formation ofan IPN reduces the ΔT_(g) between at least two of the polymericcomponents of the IPN at least about 20 percent as compared to a polymerblend including the same two polymeric components. In yet anotherembodiment, the formation of an IPN reduces the ΔT_(g) between at leasttwo of the polymeric components by at least about 35 percent, preferablyby at least about 50 percent, and more preferably by at least about 75percent as compared with a polymer blend including the same twopolymeric components. In yet another embodiment, the formation of an IPNyields only one observable T_(g) for the at least two polymericcomponents.

Alternately, in the case where at least two of the polymeric componentsof the IPN associate or interact strongly in a polymer blend, especiallythrough hydrogen-bonding, ionic aggregation, chelation, or the like, theformation of an IPN can increase the ΔT_(g) between the at least twopolymeric components in the IPN, in some cases at least about 5 percent,as compared with the ΔT_(g) between a polymer blend containing the sameat least two polymeric components. In one such alternate embodiment, theformation of an IPN increases the ΔT_(g) between at least two of thepolymeric components of the IPN at least about 10 percent. In anothersuch alternate embodiment, the formation of an IPN increases the ΔT_(g)between at least two of the polymeric components of the IPN at leastabout 20 percent.

Preferably, the formation of an IPN reduces the absolute value of thearea under the melting endotherm, often called ΔH_(f), of at least oneof the crystallizable polymeric components of the IPN at least about 5percent less than the area under the melting endotherm of a polymerblend of the same ratio of the at least one crystallizable polymericcomponent. In one embodiment, the formation of an IPN reduces ΔH_(f) ofat least one of the crystallizable polymeric components of the IPN atleast about 10 percent compared to the blend. In another embodiment, theformation of an IPN reduces ΔH_(f) of at least one of the crystallizablepolymeric components of the IPN at least about 15 percent compared tothe blend. In various other embodiments, the formation of an IPN reducesΔH_(f) of at least one of the crystallizable polymeric components of theIPN at least about 25 percent compared to the blend, at least about 50percent compared to the blend, and at least about 75 percent compared tothe blend. In yet another embodiment, the formation of an IPN results inat least one of the crystallizable polymeric components beingsubstantially free of crystallinity, as measured by ΔH_(f).

When performing DMA or DMTA experiments, ASTM D4065-95 was followed inanalyzing sample material responses. A heating rate of no more thanabout 2° C./min was employed for these tests, and the thicknesses of thesamples were kept within about 5 percent of the average thickness. Whenperforming DSC experiments to measure the glass transition temperature,T_(g), or the melting temperature, T_(pm), of samples, ASTM D3418-99 wasfollowed, in which the numerical value of T_(g) represents the mediantemperature of the transition and the numerical value of T_(pm)represents the peak extremum of the melting endotherm. When performingDSC experiments to measure the degree of crystallinity or the area underthe melting endotherm, ΔH_(f), ASTM D3417-99 was followed.

As is very often the case in multi-polymer blend systems, two of thepolymeric components may be immiscible or partially miscible, such thatphase separation occurs to a certain extent. This phase separation maybe visible to one of ordinary skill in the art (macrophase separation)or may only be observable through specialized characterizationtechniques designed to probe regions of less than about 500 microns(microphase separation). At the meeting of the at least two phases,there is a phase boundary that defines the edge of each phase. Theaverage size of the phases of each phase separated component can beexperimentally measured using, for example, atomic force microscopy,scanning electron microscopy, transmission electron microscopy, or otherappropriate characterization apparatus.

In a preferred embodiment, the formation of an IPN, in which two of thepolymeric components may be immiscible or partially miscible, results inan average phase size of each phase separated component that can beconsiderably less than the average phase size of each phase separatedcomponent in a blend of two or more of the components. In oneembodiment, the formation of an IPN results in an average phase size ofeach phase separated component being at least about 10 percent smallerthan a blend of the two components. In another embodiment, the formationof an IPN results in an average phase size of each phase separatedcomponent being at least about 20 percent smaller than a blend of thetwo components. In various other embodiments, the formation of an IPNresults in an average phase size of each phase separated component beingat least about 35 percent smaller than a blend of the two components, atleast about 60 percent smaller than a blend of the two components, andat least about 85 percent smaller than a blend of the two components. Insome cases, IPN formation can result in complete miscibility of thesystem, resulting in no discernible phase boundaries, while thecomponents may have been immiscible or only partially miscible when in ablend.

In one embodiment, the formation of an IPN increases at least one of thefollowing measurable quantities: the area under the loss modulus peak,represented by a local maximum in E″, or loss tangent peak, representedby a local maximum in tan δ; the temperature range over which the lossmodulus or loss tangent peak extends; the full-width at half-maximumheight (FWHM) of the loss modulus or loss tangent peak; or the number ofloss modulus or loss tangent peaks over a given temperature interval, ascompared to the same value(s) measured for a blend of the same ratio ofthe at least two IPN components. In another embodiment, the formation ofan IPN increases at least one of the aforementioned measurablequantities by at least about 2 percent, as compared to the same value(s)measured for a blend of the same ratio of the at least two IPNcomponents. In yet another embodiment, the formation of an IPN increasesat least one of the aforementioned measurable quantities by at leastabout 5 percent, as compared to the same value(s) measured for a blendof the same ratio of the at least two IPN components. In still anotherembodiment, the formation of an IPN increases at least one of theaforementioned measurable quantities by at feast about 10 percent, ascompared to the same value(s) measured for a blend of the same ratio ofthe at least two IPN components. In various other embodiments, theformation of an IPN increases at least one of the aforementionedmeasurable quantities by at least about 25 percent, by at least about 50percent, and by at least about 75 percent, as compared to the samevalue(s) measured for a blend of the same ratio of the at least two IPNcomponents. Alternately, instead of a comparison to the value(s)measured for a blend of the same ratio of the at least two IPNcomponents, at least one of the aforementioned measure quantities can becompared to an uncrosslinked polymer of one of the at least two IPNcomponents, a crosslinked polymer of one of the at least two IPNcomponents, a random, block, graft, or other type of copolymer of atleast two of the individual polymer components of the IPN, a crosslinkedcopolymer of at least two of the individual polymer components of theIPN, or some combination thereof.

It is also desirable for the cover, or the outermost layer of the coverif the cover has a plurality of layers, to exhibit a high shearresistance, which is manifest as the ability of a material to maintainits mechanical stability and integrity upon the application of a shearstress to that material. A “shear resistance rating” is a qualitative,or relative, scale for assessing the relative shear resistance of amaterial. The lower the shear resistance rating is, the higher the shearresistance of the material. For painted golf ball cover materials, theshear resistance rating categories from 1 to 5 are listed and describedin the table below: Description Rating No visible damage to cover orpaint 1 Paint damage only 2 Slight cover shear and/or paint damageobserved 3 Moderate cover shear; fraying; and/or slight material removed4 Extensive cover shear; heavy material removed; and/or severe 5material clumping

The shear resistance rating can be determined by using a Miya™mechanical Golf Swing Machine, commercially available from Miyamae Co.,Ltd., of Osaka, Japan, to make two hits on each of about 6 to 12substantially identical golf balls of substantially the same compositionwith either a sand wedge or a pitching wedge. First, the test conditionsare adjusted and verified so that a control golf ball having a balatacover produces a rating of 5 on the shear resistance rating scale above.Following the calibration procedure, each experimental golf ball istested and assigned a rating based upon visible manifestations of damageafter being struck. The shear resistance rating for a golf ball coverlayer of a given composition represents a numerical average of all thetested substantially identical golf balls. One alternative way to testshear resistance of a golf ball cover involves using player-testing andevaluating the results after the ball is struck multiple times withwedges and/or short irons.

In a preferred embodiment, the formation of an IPN in a layer of a golfball according to the present invention increases the shear resistanceof the cover layer of that golf ball, preferably resulting in a decreasein the shear test rating of at least 1, more preferably resulting in adecrease of at least 2, compared to the cover layer material of aconventional golf ball that is substantially free of IPN and that ismade of the same components as the IPN. In that embodiment, it ispreferred that the shear resistance of the cover layer of that golf ballhas a shear test rating of 3 or less, most preferably 2 or less.

Advantageously, the formation of an IPN in a golf ball layer may alsoincrease the resistance to moisture penetration of that layer. IPNformation in that layer may also provide reduction in the water vaporpermeability of a golf ball layer having an IPN therein. The reducedexposure of golf ball materials to water or water vapor helps inhibitdegradation of or maintain the mechanical and/or chemical properties ofthose materials. This is particularly true when the water or moisturecan facilitate degradation of molecular weight or mechanical propertiesof one or more components of the materials within the golf ball.

The ranges of values of several golf ball or material properties listedherein can vary, even outside their recited ranges, by the inclusion ofIPNs according to the invention and, if necessary, by selectivelyvarying at least one other property mentioned herein. Examples of suchgolf ball or material properties whose ranges can be varied by inclusionof an IPN include, but are not limited to, tensile or flexural modulusand impact resistance.

Golf Ball Construction

The compositions of the present invention may be used with any type ofball construction including, but not limited to, one-piece, two-piece,three-piece, and four-piece designs, a double core, a double cover, anintermediate layer(s), a multilayer core, and/or a multi-layer coverdepending on the type of performance desired of the ball. That is, thecompositions of the invention may be used in a core, an intermediatelayer, and/or a cover of a golf ball, each of which may have a singlelayer or multiple layers. As used herein, the term “multilayer” means atleast two layers.

For instance, the core may be a one-piece core or a multilayer core,both of which may be solid, semi-solid, hollow, fluid-filled, orpowder-filled. As used herein, the term “fluid” includes a liquid, apaste, a gel, a gas, or any combination thereof. A “fluid-filled” golfball center or core according to the invention also includes a hollowcenter or core. A multilayer core is one that has an innermost componentwith an additional core layer or additional core layers disposedthereon. In addition, when the golf ball of the present inventionincludes an intermediate layer, this layer may be incorporated with asingle or multilayer cover, a single or multi-piece core, with both asingle layer cover and core, or with both a multilayer cover and amultilayer core. The intermediate layer may be an inner cover layer orouter core layer, or any other layer(s) disposed between the inner coreand the outer cover of a golf ball. As with the core, the intermediatelayer, if included, and the cover layer may include a plurality oflayers. It will be appreciated that any number or type of intermediateand cover layers may be used, as desired. For example, the intermediatelayer may also be a tensioned elastomeric material wound around a solid,semi-solid, hollow, fluid-filled, or powder-filled center.

Referring to FIG. 1, a golf ball 10 of the present invention can includea center 12 and a cover 16 surrounding the center 12. Referring to FIG.2, a golf ball 20 of the present invention can include a center 22, acover 26, and at least one intermediate layer 24 disposed between thecover and the center. In one embodiment, the intermediate layer 24 isdisposed within the core, which also includes a center 22 and mayoptionally include a wound layer (not shown). In another embodiment, theintermediate layer 24 is disposed outside of the core, which mayoptionally include a wound layer (not shown), but which is disposedunder the cover layer 26. Each of the cover and center layers in FIG. 1or 2 may include more than one layer, i.e., the golf ball can be aconventional three-piece wound ball, a two-piece ball, a ball having amulti-layer core and an intermediate layer or layers, etc. Also, FIG. 3shows a golf ball 30 of the present invention including a center 32, acover 38, and an intermediate layer 34 located within the core 33.

Alternately, also referring to FIG. 3, a golf ball 30 of the presentinvention can include a center 32, a cover 38, and an intermediate layer36 disposed between the cover and the core 33. Although FIG. 3 showsgolf balls with only one intermediate layer, it will be appreciated thatany number or type of intermediate layers may be used whether inside oroutside the core, or both, as desired. Further, any of the figuresdetailed herein may include embodiments wherein an optional wound layeris disposed between the center and the core of the golf ball.

Other non-limiting examples of suitable types of ball constructions thatmay be used with the present invention include those described in U.S.Pat. Nos. 6,056,842, 5,688,191, 5,713,801, 5,803,831, 5,885,172,5,919,100, 5,965,669, 5,981,654, 5,981,658, and 6,149,535, as well as inPublication Nos. US2001/0009310 A1, US2002/0025862, and US2002/0028885.The entire disclosures of these patents and published patentapplications are incorporated by reference herein.

Layer Compositions

Golf Ball Core Layer(s)

The cores of the golf balls formed according to the invention may besolid, semi-solid, hollow, fluid-filled or powder-filled, one-piece ormulti-component cores. As used herein, the terms core and center aregenerally used interchangeably to reference the innermost component ofthe ball. In some embodiments, however, the term “center” is used whenthere are multiple core layers, i.e., a center and an outer core layer.The term “semi-solid” as used herein refers to a paste, a gel, or thelike.

Any core material known to one of ordinary skill in that art is suitablefor use in the golf balls of the invention. Suitable core materialsinclude thermoset materials, such as rubber, styrene butadiene,polybutadiene, isoprene, polyisoprene, trans-isoprene, as well asthermoplastics such as ionomer resins, polyamides or polyesters, andthermoplastic and thermoset polyurethane elastomers. For example,butadiene rubber, which, in an uncured state, typically has a Mooneyviscosity greater than about 20, preferably greater than about 30, andmore preferably greater than about 40, may be used in one or more corelayers of the golf balls prepared according to the present invention.Mooney viscosity is typically measured according to ASTM D1646-99. Inaddition, the IPNs of the present invention may also be incorporatedinto any component of a golf ball, including the core.

A free-radical source, often alternatively referred to as a free-radicalinitiator, may optionally be used in the core, or one or more layers ofthe golf balls according to the invention, particularly when a polymercomponent includes a thermoset material. The free-radical source fornon-IPN components may be similar to that used in an IPN of the presentinvention or may be selected from the same or other suitable compounds.

The free radical source for non-IPN components is preferably a peroxide,more preferably an organic peroxide. The peroxide is typically presentin an amount greater than about 0.1 parts per hundred of the totalpolymer component, preferably about 0.1 to 15 parts per hundred of thepolymer component, and more preferably about 0.2 to 5 parts per hundredof the total polymer component. It should be understood by those ofordinary skill in the art that the presence of certain components mayrequire a larger amount of free-radical source than the amountsdescribed herein. The free radical source may alternatively oradditionally be one or more of an electron beam, UV or gamma radiation,x-rays, or any other high energy radiation source capable of generatingfree radicals. It should be further understood that heat oftenfacilitates initiation of the generation of free radicals when peroxidesare used as a free-radical initiator.

Golf Ball Intermediate Layer(s)

When the golf ball of the present invention includes an intermediatelayer, such as an inner cover layer or outer core layer, i.e., anylayer(s) disposed between the inner core and the outer cover of a golfball, this layer can include any materials known to those of ordinaryskill in the art including thermoplastic and thermosetting materials. Inone embodiment, the intermediate layer is formed, at least in part, froman IPN of the invention.

The intermediate layer(s) may also be formed, at least in part, from oneor more homopolymeric or copolymeric materials, such as ionomers,primarily or fully non-ionomeric thermoplastic materials, vinyl resins,polyolefins, polyurethanes, polyureas, such as those disclosed in U.S.Pat. No. 5,484,870, polyamides, acrylic resins and blends thereof,olefinic thermoplastic rubbers, block copolymers of styrene andbutadiene, isoprene or ethylene-butylene rubber, copoly(ether-amide),such as PEBAX, sold by Atofina Chemicals, Inc. of Philadelphia, Pa.,polyphenylene oxide resins or blends thereof, and thermoplasticpolyesters.

For example, the intermediate layer may be formed of low acid ionomers,such as those described in U.S. Pat. Nos. 6,506,130 and 6,503,156, highacid ionomers, highly neutralized polymers, such as those disclosed inU.S. Patent Publication Nos. 2001/0018375 and 2001/0019971, or mixturesthereof. The intermediate layer may also be formed from the compositionsas disclosed in U.S. Pat. No. 5,688,191. The entire disclosures of thesepatents and publications are incorporated herein by express referencethereto.

The intermediate layer may also include a wound layer formed from atensioned thread material. Many different kinds of thread materials maybe used for the wound layer of the present invention. The thread may besingle-ply or may include two or more plies. Preferably, the thread ofthe present invention is single-ply. The thread may be selected to havedifferent material properties, dimensions, cross-sectional shapes, andmethods of manufacturing. If two or more threads are used, they may beidentical in material and mechanical properties or they may besubstantially different from each other, either in cross-section shapeor size, composition, elongated state, and mechanical or thermalproperties. Mechanical properties that may be varied include resiliency,elastic modulus, and density. Thermal properties that may be variedinclude melt temperature, glass transition temperature and thermalexpansion coefficient.

The tensioned thread material of the wound layer may encompass anysuitable material, but typically includes fiber, glass, carbon,polyether urea, polyether block copolymers, polyester urea, polyesterblock copolymers, syndiotactic- or isotactic-poly(propylene),polyethylene, polyamide, poly(oxymethylene), polyketone, poly(ethyleneterephthalate), poly(p-phenylene terephthalamide), poly(acrylonitrile),diaminodicyclohexylmethane, dodecanedicarboxylic acid, natural rubber,polyisoprene rubber, styrene-butadiene copolymers,styrene-propylene-diene copolymers, another synthetic rubber, or block,graft, random, alternating, brush, multi-arm star, branched, ordendritic copolymers, or mixtures thereof.

Threads used in the present invention may be formed using a variety ofprocesses including conventional calendering and slitting, meltspinning, wet spinning, dry spinning and polymerization spinning. Anyprocess available to one of ordinary skill in the art may be employed toproduce thread materials for use in the wound layer. The tension used inwinding the thread material of the wound layer may be selected asdesired to provide beneficial playing characteristics to the final golfball. The winding tension and elongation may be kept the same or may bevaried throughout the layer. Preferably, the winding occurs at aconsistent level of tension so that the wound layer has consistenttension throughout the layer.

In addition, the winding patterns used for the wound layer can be variedin any way available to those of ordinary skill in the art. Although oneor more threads may be combined to begin forming the wound layer, it ispreferred to use only a single continuous thread.

Golf Ball Cover(s)

The cover provides the interface between the ball and a club. Propertiesthat are desirable for the cover are good moldability, high abrasionresistance, high impact resistance, high tear strength, high resilience,and good mold release, among others. The cover layer may be formed, atleast in part, from an IPN of the invention.

When an IPN of the invention is incorporated into a core orintermediate/inner cover layer, the cover compositions may include oneor more homopolymeric or copolymeric materials as discussed in thesection above pertaining to the intermediate layer. The cover may alsobe at least partially formed from the polybutadiene reaction productdiscussed above with respect to the core.

As discussed elsewhere herein, the cover may be molded onto the golfball in any known manner, such as by casting, compression molding,injection molding, reaction injection molding, or the like. One skilledin the art would appreciate that the molding method used may bedetermined at least partially by the properties of the composition. Forexample, casting may be preferred when the material is thermoset,whereas compression molding or injection molding may be preferred forthermoplastic compositions.

The golf balls of the present invention can likewise include one or morehomopolymeric or copolymeric thermoplastic or thermoset materials in acenter, an intermediate layer, and/or a cover, either individually or incombination with any other available materials or in a blend with anyIPN according to the invention. In one embodiment, the one or moreportions of the ball including IPN material will not include blends withconventional materials. One of ordinary skill in the art would know thatmost of the polymeric materials listed below may belong in thethermoplastic category or in the thermoset category, depending upon thenature of the repeat units, functional groups pendant from the repeatunits, method of polymerization, method of formation, temperature offormation, post-polymerization treatments, and/or many other possiblefactors, and are suitable for use in golf balls according to theinvention. The materials include, but are not limited to, the followingpolymers, or their set of monomeric, oligomeric, or macromonomericprecursors:

(1) Vinyl resins, for example, such as those formed by thepolymerization of vinyl chloride, or by the copolymerization of vinylchloride with vinyl acetate, acrylic esters or vinylidene chloride;

(2) Polyolefins, for example, such as polyethylene, polypropylene,polybutylene, and copolymers, such as ethylene methylacrylate, ethyleneethylacrylate, ethylene vinyl acetate, ethylene methacrylic acid,ethylene acrylic acid, or propylene acrylic acid, as well as copolymersand homopolymers, such as those produced using a single-site catalyst ora metallocene catalyst;

(3) Polyurethanes, for example, such as those prepared from diols,triols, or polyols and diisocyanates, triisocyanates, orpolyisocyanates, as well as those disclosed in U.S. Pat. No. 5,334,673;

(4) Polyureas, for example, such as those prepared from diamines,triamines, or polyamines and diisocyanates, triisocyanates, orpolyisocyanates, as well as those disclosed in U.S. Pat. No. 5,484,870;

(5) Polyamides, for example, such as poly(hexamethylene adipamide) andothers prepared from diamines and dibasic acids, as well as those fromamino acids such as poly(caprolactam), and blends of polyamides withSURLYN, polyethylene, ethylene copolymers,ethyl-propylene-non-conjugated diene terpolymer, and the like;

(6) Acrylic resins and blends of these resins with, for example,polymers such as poly vinyl chloride, elastomers, and the like;

(7) Olefinic rubbers, for example, such as blends of polyolefins withethylene-propylene-non-conjugated diene terpolymer; block copolymers ofstyrene and butadiene, isoprene or ethylene-butylene rubber; orcopoly(ether-amide), such as PEBAX, sold by ELF Atochem of Philadelphia,Pa.;

(8) Polyphenylene oxide resins or blends of polyphenylene oxide withhigh impact polystyrene, for example, as sold under the trademark NORYLby General Electric Company of Pittsfield, Mass.;

(9) Polyesters, for example, such as polyethylene terephthalate,polybutylene terephthalate, polyethylene terephthalate/glycol modifiedand elastomers, such as sold under the trademarks HYTREL by E.I. DuPontde Nemours & Co. of Wilmington, Del., and LOMOD by General ElectricCompany of Pittsfield, Mass.;

(10) Blends and alloys, for example including polycarbonate withacrylonitrile butadiene styrene, polybutylene terephthalate,polyethylene terephthalate, styrene maleic anhydride, polyethylene,elastomers, and the like, and polyvinyl chloride with acrylonitrilebutadiene styrene, ethylene vinyl acetate, or other elastomers;

(11) Blends of vulcanized, unvulcanized, or non-vulcanizable rubberswith polyethylene, propylene, polyacetal, nylon, polyesters, celluloseesters, and the like; and

(12) Polymers or copolymers possessing epoxy-containing, orpost-polymerization epoxy-functionalized, repeat units, for example, incombination with anhydride, ester, amide, amine, imide, carbonate,ether, urethane, urea, α-olefin, conjugated, or acid (optionally totallyor partially neutralized with inorganic salts), such as HPF-1000 andHPF-2000 commercially available from DuPont, comonomers, or copolymersor blends thereof.

Layer Formation

The golf balls of the invention may be formed using a variety ofapplication techniques such as compression molding, flip molding,injection molding, retractable pin injection molding, reaction injectionmolding (RIM), liquid injection molding (LIM), casting, vacuum forming,powder coating, flow coating, spin coating, dipping, spraying, and thelike. Conventionally, compression molding and injection molding areapplied to thermoplastic materials, whereas RIM, liquid injectionmolding, and casting are employed on thermoset materials. These andother manufacture methods are disclosed in U.S. Pat. Nos. 6,207,784 and5,484,870, the disclosures of which are incorporated herein by referencein their entirety.

The cores of the invention may be formed by any suitable method known tothose of ordinary skill in art. When the cores are formed from athermoset material, compression molding is a particularly suitablemethod of forming the core. In a thermoplastic core embodiment, on theother hand, the cores may be injection molded. Furthermore, U.S. Pat.Nos. 6,180,040 and 6,180,722 disclose methods of preparing dual coregolf balls. The disclosures of these patents are hereby incorporated byreference in their entirety.

The intermediate layer may also be formed from using any suitable methodknown to those of ordinary skill in the art. For example, anintermediate layer may be formed by blow molding and covered with adimpled cover layer formed by injection molding, compression molding,casting, vacuum forming, powder coating, and the like. In oneembodiment, the intermediate layer may be a moisture barrier layer asdisclosed in U.S. Pat. No. 6,632,147. Thus, a golf ball of the inventionmay include an intermediate layer that has a moisture vapor transmissionrate lower than that of the cover and, additionally, a primaryingredient of the intermediate layer is made from a material includingpolybutadiene, natural rubber, butyl-based rubber, acrylics,trans-polyisoprene, neoprene, chlorinated polyethylene, balata,multi-layer thermoplastic films, blends of ionomers, polyvinyl alcoholcopolymer and polyamides, and dispersions of acid salts ofpolyetheramines.

The IPNs of the invention may be applied over an inner ball using avariety of application techniques such as spraying, compression molding,dipping, spin coating, casting, or flow coating methods that are wellknown in the art. In one embodiment, the IPNs are formed over the coreusing a combination of casting and compression molding. In addition, theIPNs may be formed around an inner ball using reaction injection molding(RIM) and liquid injection molding (LIM) techniques.

The use of various dimple patterns and profiles provides a relativelyeffective way to modify the aerodynamic characteristics of a golf ball.As such, the manner in which the dimples are arranged on the surface ofthe ball can be by any available method. For instance, the ball may havean icosahedron-based pattern, such as described in U.S. Pat. No.4,560,168, or an octahedral-based dimple patterns as described in U.S.Pat. No. 4,960,281. The resultant golf balls prepared according to theinvention typically will have dimple coverage greater than about 60percent, preferably greater than about 65 percent, and more preferablygreater than about 70 percent.

Golf Ball Post-Processing

The golf balls of the present invention may be painted, coated, orsurface treated for further benefits. For example, golf balls may becoated with the IPNs of the invention in order to obtain an extremelysmooth, tack-free surface. In addition to the IPNs of the invention,other coating materials, such as urethanes, urethane hybrids, epoxies,polyesters and acrylics, may be used for coating golf balls formedaccording to the invention. If desired, more than one coating layer canbe used. The coating layer(s) may be applied by any suitable methodknown to those of ordinary skill in the art. In one embodiment, thecoating layer(s) is applied to the golf ball cover by an in-mold coatingprocess, such as described in U.S. Pat. No. 5,849,168, which isincorporated in its entirety by reference herein.

Golf Ball Properties

The properties such as core diameter, intermediate layer thickness andcover layer thickness, hardness, and compression have been found toeffect play characteristics such as spin, initial velocity and feel ofthe present golf balls.

Component Dimensions

Dimensions of golf ball components, i.e., thickness and diameter, mayvary depending on the desired properties. For the purposes of theinvention, any layer thickness may be employed. For example, the presentinvention relates to golf balls of any size, although the golf ballpreferably meets USGA standards of size and weight. While “The Rules ofGolf” by the USGA dictate specifications that limit the size of acompetition golf ball to more than 1.680 inches in diameter, golf ballsof any size can be used for leisure golf play. The preferred diameter ofthe golf balls is from about 1.680 inches to about 1.800 inches. Themore preferred diameter is from about 1.680 inches to about 1.760inches. A diameter of from about 1.680 inches (43 mm) to about 1.740inches (44 mm) is most preferred, however diameters anywhere in therange of from 1.700 to about 1.950 inches can be used. Preferably, theoverall diameter of the core and all intermediate layers is about 80percent to about 98 percent of the overall diameter of the finishedball.

The core may have a diameter ranging from about 0.09 inches to about1.65 inches. In one embodiment, the diameter of the core of the presentinvention is about 1.2 inches to about 1.630 inches. In anotherembodiment, the diameter of the core is about 1.3 inches to about 1.6inches, preferably from about 1.39 inches to about 1.6 inches, and morepreferably from about 1.5 inches to about 1.6 inches. In yet anotherembodiment, the core has a diameter of about 1.55 inches to about 1.65inches. In one embodiment, the core diameter is about 1.59 inches orgreater. In another embodiment, the diameter of the core is about 1.64inches or less.

When the core includes an inner core layer and an outer core layer, theinner core layer is preferably about 0.9 inches or greater and the outercore layer preferably has a thickness of about 0.1 inches or greater. Inone embodiment, the inner core layer has a diameter from about 0.09inches to about 1.2 inches and the outer core layer has a thickness fromabout 0.1 inches to about 0.8 inches. In yet another embodiment, theinner core layer diameter is from about 0.095 inches to about 1.1 inchesand the outer core layer has a thickness of about 0.20 inches to about0.03 inches.

The cover typically has a thickness to provide sufficient strength, goodperformance characteristics, and durability. In one embodiment, thecover thickness is from about 0.02 inches to about 0.12 inches,preferably about 0.1 inches or less. In another embodiment, the coverthickness is about 0.05 inches or less, preferably from about 0.02inches to about 0.05 inches, and more preferably about 0.02 inches andabout 0.045 inches.

The range of thicknesses for an intermediate layer of a golf ball islarge because of the vast possibilities when using an intermediatelayer, i.e., as an outer core layer, an inner cover layer, a woundlayer, a moisture/vapor barrier layer. When used in a golf ball of theinvention, the intermediate layer, or inner cover layer, may have athickness about 0.3 inches or less. In one embodiment, the thickness ofthe intermediate layer is from about 0.002 inches to about 0.1 inches,preferably about 0.01 inches or greater. In another embodiment, theintermediate layer thickness is about 0.05 inches or less, morepreferably about 0.01 inches to about 0.045 inches.

Hardness

The golf ball layers containing the IPNs according to the presentinvention typically have a material hardness greater than about 15 ShoreA, preferably from about 15 Shore A to 85 Shore D. In one preferredembodiment, the material hardness of a golf ball layer including an IPNof the present invention is from about 10 to 85 Shore D. It should beunderstood, especially to one of ordinary skill in the art, that thereis a fundamental difference between “material hardness” and “hardness,as measured directly on a golf ball.” Material hardness is defined bythe procedure set forth in ASTM-D2240-00 and generally involvesmeasuring the hardness of a flat “slab” or “button” formed of thematerial of which the hardness is to be measured. Generally,ASTM-D2240-00 requires calibration of durometers, which have scalereadings from 0 to 100. However, readings below 10 or above 90 are notconsidered reliable, as noted in ASTM-D2240-00, and accordingly, all thehardness values herein are within this range.

In particular, the cores of the present invention may have varyinghardnesses depending on the particular golf ball construction. In oneembodiment, the core hardness is at least about 15 Shore A, preferablyabout 30 Shore A, as measured on a formed sphere. In another embodiment,the core has a hardness of about 50 Shore A to about 90 Shore D. In yetanother embodiment, the hardness of the core is about 80 Shore D orless. Preferably, the core has a hardness about 30 to about 65 Shore D,and more preferably, the core has a hardness about 35 to about 60 ShoreD.

The intermediate layer(s) of the present invention may also vary inhardness depending on the specific construction of the ball. In oneembodiment, the hardness of the intermediate layer is about 30 Shore Dor greater. In another embodiment, the hardness of the intermediatelayer is about 90 Shore D or less, preferably about 80 Shore D or less,and more preferably about 70 Shore D or less. In yet another embodiment,the hardness of the intermediate layer is about 50 Shore D or greater,preferably about 55 Shore D or greater. In one embodiment, theintermediate layer hardness is from about 55 Shore D to about 65 ShoreD. The intermediate layer may also be about 65 Shore D or greater.

As with the core and intermediate layers, the cover hardness may varydepending on the construction and desired characteristics of the golfball. The ratio of cover hardness to inner ball hardness is a primaryvariable used to control the aerodynamics of a ball and, in particular,the spin of a ball. In general, the harder the inner ball, the greaterthe driver spin and the softer the cover, the greater the driver spin.

For example, when the intermediate layer is intended to be the hardestpoint in the ball, e.g., about 50 Shore D to about 75 Shore D, the covermaterial may have a hardness of about 20 Shore D or greater, preferablyabout 25 Shore D or greater, and more preferably about 30 Shore D orgreater, as measured on the slab. In another embodiment, the coveritself has a hardness of about 30 Shore D or greater. In particular, thecover may be from about 30 Shore D to about 70 Shore D. In oneembodiment, the cover has a hardness of about 40 Shore D to about 65Shore D, and in another embodiment, about 40 Shore to about 55 Shore D.In another aspect of the invention, the cover has a hardness less thanabout 45 Shore D, preferably less than about 40 Shore D, and morepreferably about 25 Shore D to about 40 Shore D. In one embodiment, thecover has a hardness from about 30 Shore D to about 40 Shore D.

Compression

Compression values are dependent on the diameter of the component beingmeasured. The Atti compression of the core, or portion of the core, ofgolf balls prepared according to the invention is preferably less thanabout 80, more preferably less than about 75. As used herein, the terms“Atti compression” or “compression” are defined as the deflection of anobject or material relative to the deflection of a calibrated spring, asmeasured with an Atti Compression Gauge, that is commercially availablefrom Atti Engineering Corp. of Union City, N.J. Atti compression istypically used to measure the compression of a golf ball. In anotherembodiment, the core compression is from about 40 to about 80,preferably from about 50 to about 70. In yet another embodiment, thecore compression is preferably below about 50, and more preferably belowabout 25.

In an alternative, low compression embodiment, the core has acompression less than about 20, more preferably less than about 10, andmost preferably, 0. As known to those of ordinary skill in the art,however, the cores generated according to the present invention may bebelow the measurement of the Atti Compression Gauge.

In one embodiment, golf balls of the invention preferably have an Atticompression of about 55 or greater, preferably from about 60 to about120. In another embodiment, the Atti compression of the golf balls ofthe invention is at least about 40, preferably from about 50 to 120, andmore preferably from about 60 to 100. In yet another embodiment, thecompression of the golf balls of the invention is about 75 or greaterand about 95 or less. For example, a preferred golf ball of theinvention may have a compression from about 80 to about 95.

Coefficient of Restitution

The present invention contemplates golf balls having CORs from about0.700 to about 0.850 at an inbound velocity of about 125 ft/sec. In oneembodiment, the COR is about 0.750 or greater, preferably about 0.780 orgreater. In another embodiment, the ball has a COR of about 0.800 orgreater. In yet another embodiment, the COR of the balls of theinvention is about 0.800 to about 0.815.

Alternatively, the maximum COR of the ball is one that does not causethe golf ball to exceed initial velocity requirements established byregulating entities such as the USPGA. As used herein, the term“coefficient of restitution” (CoR) is calculated by dividing the reboundvelocity of the golf ball by the incoming velocity when a golf ball isshot out of an air cannon. The COR testing is conducted over a range ofincoming velocities and determined at an inbound velocity of 125 ft/s.Another measure of this resilience is the “loss tangent,” or tan δ,which is obtained when measuring the dynamic stiffness of an object.Loss tangent and terminology relating to such dynamic properties istypically described according to ASTM D4092-90. Thus, a lower losstangent indicates a higher resiliency, thereby indicating a higherrebound capacity. Low loss tangent indicates that most of the energyimparted to a golf ball from the club is converted to dynamic energy,i.e., launch velocity and resulting longer distance. The rigidity orcompressive stiffness of a golf ball may be measured, for example, bythe dynamic stiffness. A higher dynamic stiffness indicates a highercompressive stiffness. To produce golf balls having a desirablecompressive stiffness, the dynamic stiffness of the crosslinked materialshould be less than about 50,000 N/m at −50° C. Preferably, the dynamicstiffness should be between about 10,000 and 40,000 N/m at −50° C., morepreferably, the dynamic stiffness should be between about 20,000 and30,000 N/m at −50° C.

Spin Rate

A spin rate of a golf ball refers to the speed it spins on an axis whilein flight, measured in revolutions per minute (“rpm”). Spin generateslift, and accordingly, spin rate directly influences how high the ballflies and how quickly it stops after landing. The golf balls disclosedherein can be tested to determine spin rate by initially establishingtest conditions using suitable control golf balls and golf clubs. Forexample, a spin rate of a golf ball struck by a standard golf driver wasobtained by using test conditions for a Titleist Pinnacle Gold golf ballthat gives a ball speed of about 159 to about 161 miles/hour, a launchangle of about 9.0 degrees to about 10.0 degrees, and a spin rate ofabout 2900 rpm to about 3100 rpm. Thus in one embodiment, the spin rateof a golf ball hit with a golf club driver under the same testconditions is between about 1200 rpm to about 4000 rpm. In a preferredembodiment, the spin rate of a golf ball hit with a golf club driver isbetween about 2000 rpm to about 3500 rpm, more preferably between about2500 and 3000 rpm.

For an 8-iron ball spin test, a spin rate of a golf ball struck by astandard 8-iron club was obtained by using test conditions for aTitleist Pro VI golf ball that gives a ball speed of about 114 to about116 miles/hour, a launch angle of about 18.5 to about 19.5 degrees and aspin rate of about 8100 rpm to about 8300 rpm. Thus in one embodiment,the spin rate of an average, cleanly struck 8-iron shot is between 6500rpm and 10,000 rpm. In preferred embodiment, the spin rate of anaverage, cleanly struck 8-iron shot under the same test conditions isbetween 7500 rpm and 9500 rpm, more preferably between about 8000 rpmand 9000 rpm.

Moisture Vapor Transmission

The moisture vapor transmission of a golf ball portion formed from thecompositions of the invention may be expressed in terms of absorption,e.g., weight gain or size gain over a period of time at a specificconditions, and transmission, e.g., moisture vapor transmission rate(MVTR) according to ASTM E96-00. MVTR refers to the mass of water vaporthat diffused into a material of a given thickness per unit area perunit time at a specific temperature and humidity differential. Forexample, weight changes of a golf ball portion monitored over a periodof seven weeks in 100 percent relative humidity and 72° F. help todemonstrate which balls have better water resistance. In one embodiment,the golf ball portions of the invention have a weight gain of about 0.15grams or less after seven weeks. In another embodiment, the golf ballsof the invention have a weight gain of about 0.13 grams or less after aseven-week storage period. In still another embodiment, the weight gainof the golf balls of the invention is about 0.09 grams or less afterseven weeks. In yet another embodiment, the weight gain is about 0.06grams or less after a seven-week period. The golf balls of the inventionpreferably have a weight gain of about 0.03 grams or less over aseven-week storage period.

Size gain may also be used as an indicator of water resistance. That is,the more water a golf ball takes on, the larger a golf ball becomes dueto the water enclosed beneath the outermost layer of the golf ballportion. Thus, the golf balls of the invention preferably have noappreciable size gain. In one embodiment, the size gain of the golfballs of the invention after a seven-week period is about 0.001 inchesor less.

MVTR of a golf ball, or portion thereof, may be about 2 g/(m2×day) orless, such as about 0.45 to about 0.95 g/(m2×day), about 0.01 to about0.9 g/(m2×day) or less, at 38° C. and 90 percent relative humidity.

EXAMPLES

The following examples are only representative of the methods andmaterials for use in golf ball compositions and golf balls of thisinvention, and are not to be construed as limiting the scope of theinvention in any way.

Example 1 Golf Ball Having a Urethane-Epoxy IPN Present in the CoverLayer

The golf ball of Example 1 was prepared with a 1.585 inch (about 4.03cm) wound core around a fluid-filled center. The golf ball had afinished diameter of about 1.68 inches (about 4.27 cm). The golf ball ofExample 1 included an IPN of a polyurethane and an epoxy polymer,wherein the epoxy polymer component was about 5 percent of the IPN andthe polyurethane component was about 95 percent of the IPN. The urethaneprecursor package in Example 1 included Vibrathane B-821 prepolymer,1,4-butanediol, and T-12 dibutyltin dilaurate catalyst. The molarproportion of isocyanate groups in the Vibrathane prepolymer to hydroxylgroups in the diol was in about a 1:0.95 ratio. The epoxy precursorpackage included an epoxy resin (DER 331) and a BF₃ catalyst/curingagent to facilitate self-polymerization and self-crosslinking to form anepoxy network. In order to limit the possibility of the polyurethanebeing further chain extended with the curing agent intended for curingthe epoxy component, the epoxy curing agent was chosen to be catalyticand substantially unreactive with the polyurethane component. The epoxycuring agent chosen to prepare the ball of Example 1 was aBF₃:4-chlorobenzenamine catalyst complex. Other epoxy curing agentsinclude, but are not limited to, oxides, such as magnesium oxide, oraluminum oxide; tertiary amines, such as N,N-dimethylaminopyridine, orbenzyldimethylamine; imidazoles, such as 2-ethyl-4-methylimidazole; andphosphines, such as triphenylphosphine, or tributylphosphine.

The respective precursor packages were mixed separately until asufficient viscosity was achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages were mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 1. The total gelation time was about 80 seconds. TABLE 1Cover/Ball Characteristics Control Example 1 Urethane component BDVibrathane/BD (1:0.95) + 0.01 Vibrathane/BD (1:0.95) + 0.01 precursorpackage percent T-12 catalyst percent T-12 catalyst (95 percent) Epoxycomponent precursor — DER 331/10 pph BF₃ package catalyst (5 percent)Coefficient of Restitution 0.81 0.81 Corrected Compression 87 90Material Hardness 38 31 (Shore D) Cover Hardness (Shore D) 46 43 InitialVelocity (ft/sec) 255.5 255 T_(g) peak (° C., measured by −71 −67 DSC)T_(g) width (° C., measured by 17 24 DSC)Vibrathane is an isocyanate end-capped polyurethane prepolymer, in thiscase VIBRATHANE B-821, which is made from MDI and a 2,000 M_(N) PTMEGpolyol and is available commercially from Crompton Uniroyal ChemicalCompany, Inc., of Middlebury, Conn.; BD represents 1,4-butanediol, whichis available commercially from BASF of Parsippany, N.J.; T-12 representsa dibutyl tin dilaurate catalyst, which is available commercially fromAir Products of Allentown, Pa.; DER # 331 represents an epoxy resinbased on a diglycidyl ether of bisphenol A (DGEBA) and is commerciallyavailable from Dow Chemical Company of Midland, Mich.; BF₃ catalystrepresents a trifluoroboron-4-chlorobenzenamine catalyst complex and iscommercially available from Air Products of Allentown, Pa.

Example 2 Golf Ball Having a Urethane-Polybutadiene Diacrylate IPNPresent in the Cover Layer

The golf ball of Example 2 includes an IPN of a polyurethane and apolybutadiene copolymer, which is prepared with a 1.585 inch (about 4.03cm) wound core around a fluid-filled center. Note that the IPN'sdisclosed in the Examples and specification herein can be used in anygolf ball construction. The golf ball has a finished diameter of about1.68 inches (about 4.27 cm). The golf ball of Example 2 includes an IPNof a polyurethane and a polybutadiene diacrylate copolymer, wherein thepolybutadiene copolymer component is about 10 percent of the IPN and thepolyurethane component is about 90 percent of the IPN. The urethaneprecursor package in Example 2 includes Vibrathane B-821 prepolymer,1,4-butanediol, and T-12 dibutyltin dilaurate catalyst. The molarproportion of isocyanate groups in the Vibrathane prepolymer to hydroxylgroups in the diol is in about a 1:0.95 ratio. The polybutadienediacrylate copolymer precursor package includes butadiene monomer or apolybutadiene resin, a diacrylate crosslinking agent, and an initiatorto facilitate crosslinking to form a polybutadiene diacrylate network.In order to limit the possibility of degradation of, or interferencewith, the polyurethane chain extension reaction, the polybutadienediacrylate copolymer crosslinking initiator preferably is chosen to besubstantially unreactive with the polyurethane. The initiator chosen toprepare the ball of Example 2 is a peroxide initiator, particularlydibenzoyl peroxide.

The respective precursor packages are mixed separately until asufficient viscosity is achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages are mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 2.

Example 3 Golf Ball Having a Urethane-Acrylate IPN Present in the CoverLayer

The golf ball of Example 3 is prepared with a 1.585 inch (about 4.03 cm)wound core around a fluid-filled center. Again, note that the IPN'sdisclosed in the Examples and specification herein can be used in anygolf ball construction. The golf ball has a finished diameter of about1.68 inches (about 4.27 cm). The golf ball of Example 3 includes an IPNof a polyurethane and an acrylate polymer, wherein the acrylate polymercomponent is about 10 percent of the IPN and the polyurethane componentis about 90 percent of the IPN. The urethane precursor package inExample 3 includes Vibrathane B-821 prepolymer, 1,4-butanediol, and T-12dibutyltin dilaurate catalyst. The molar proportion of isocyanate groupsin the Vibrathane prepolymer to hydroxyl groups in the diol is in abouta 1:0.95 ratio. The acrylate precursor package includes methylmethacrylate monomer, optionally a crosslinking agent (such as adiacrylate), and an initiator to facilitate polymerization (andoptionally crosslinking) to form a methyl methacrylate polymer (andoptionally network). In order to limit the possibility of degradationof, or interference with, the polyurethane chain extension reaction, themethyl methacrylate polymerization initiator is chosen to preferably besubstantially unreactive with the polyurethane. The initiator chosen toprepare the ball of Example 3 is a free radical initiator, such asazobisisobutyronitrile (AIBN).

The respective precursor packages are mixed separately until asufficient viscosity is achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages are mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 3.

Example 4 Golf Ball Having a Urethane-Epoxy IPN Present in the CoverLayer

The golf ball of Example 4 is prepared with a 1.585 inch (about 4.03 cm)wound core around a fluid-filled center. Yet again, note that the IPN'sdisclosed in the Examples and specification herein can be used in anygolf ball construction. The golf ball has a finished diameter of about1.68 inches (about 4.27 cm). The golf ball of Example 4 includes an IPNof a polyurethane and an epoxy polymer, wherein the epoxy polymercomponent is about 10 percent of the IPN and the polyurethane componentis about 90 percent of the IPN. The urethane precursor package inExample 4 includes Vibrathane B-821 prepolymer, 1,4-butanediol, andoptionally a catalyst, such as T-12 dibutyltin dilaurate. The molarproportion of isocyanate groups in the Vibrathane prepolymer to hydroxylgroups in the diol is in about a 1:0.95 ratio. The epoxy precursorpackage includes an epoxy resin (DER 331), a BF₃ catalyst/curing agentto facilitate self-polymerization and self-crosslinking to form an epoxynetwork, and a catalyst to facilitate occasional interreactions of theurethane and the epoxy precursors or networks in the form of oxazolidonefunctional groups. In order to limit the possibility of the polyurethanebeing further chain extended with the curing agent intended for curingthe epoxy component, the epoxy curing agent is chosen to preferably becatalytic and substantially unreactive with the polyurethane component.The epoxy curing agent chosen to prepare the ball of Example 4 is aBF₃:4-chlorobenzenamine catalyst complex. The oxazolidone formationcatalyst chosen to prepare the ball of Example 4 is ethylmethylimidazole.

The respective precursor packages are mixed separately until asufficient viscosity is achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages are mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 4.

Example 5 Electron Beam Cure of Polyurea Prepolymer/Urea Acrylate

Various mixtures containing polyurea prepolymer/curative and ureaacrylate were cured using either electron beam radiation or thermalradiation and the DMA of resulting interpenetrating polymer networkswere analyzed and compared with respect to their crosslink density. Thecurative in the polyurea prepolymer/curative mixture is CLEARLINK 1000,which can have a polyurea prepolymer/curative mixture ratio of betweenabout 1:0.75 to about 1:1.25. The DMA results of the IPNs were obtainedusing a TA Instruments 2980 unit, using the following parameters:tensile film mode; 20 μm amplitude; 1 Hz frequency; 10 cNm clampingforce; −100 to 250° C.; 3° C./min heating rate; and 15×6.5×0.6 (mm)sampling dimensions. The sample compositions are summarized below inTable 2 and the DMA results are summarized below in Table 3. TABLE 2Amount of Polyurea Amount of Prepolymer/Clearlink 1000 Urea AcrylateSample ID (percent) (percent)  0 percent IPN 100 0 10 percent IPN 90 1020 percent IPN 80 20 30 percent IPN 70 30 40 percent IPN 60 40 100percent IPN  0 100

TABLE 3 Relative Relative DMA Tg Crosslink density* DMA Tg DMA TgCrosslink density* (° C.) (1000 moles/cc) (° C.) (° C.) (1000 moles/cc)Sample ID Thermal Cure Thermal Cure Before Radiation Radiation CureRadiation Cure 0 percent −44° C., 80° C. — −50° C., 71° C. −50° C., 73°C. — IPN 10 percent −47° C., 81° C. — −42° C., 70° C. −41° C., 74° C., —IPN 120° C. 20 percent −46° C., 72° C., — −48° C. −50° C., 72° C.,0.01387 IPN 135° C. 104° C. 30 percent −46° C., 72° C., 0.00358 −37° C.,43° C. −42° C., 70° C., 0.0243 IPN 131° C. 111° C. 40 percent −46° C.,66° C., 0.0124 — −42° C., 66° C. 0.058 IPN 121° C. 100 percent −50° C.,73° C. 0.83 — −42° C., 62° C. 0.5588 IPN*Relative crosslink density is a crosslink density in the sample ascompared to 0 percent IPN crosslink density.

Other than in the operating examples, or unless otherwise expresslyspecified, all of the numerical ranges, amounts, values and percentagessuch as those for amounts of materials, times and temperatures ofreaction, ratios of amounts, values for molecular weight (whether numberaverage molecular weight (“M_(n)”) or weight average molecular weight(“M_(w)”), and others in the following portion of the specification maybe read as if prefaced by the word “about” even though the term “about”may not expressly appear with the value, amount or range. Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties sought to be obtained bythe present invention. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

The invention described and claimed herein is not to be limited in scopeby the specific embodiments herein disclosed, since these embodimentsare intended as illustrations of several aspects of the invention. Anyequivalent embodiments are intended to be within the scope of thisinvention. For example, although the disclosure herein focuses on amethod of making an IPN layer for golf balls, it is also easilyapplicable by one of ordinary skill in the art to the manufacture ofother items, such as curing adhesives (e.g., in golf shoes), IPNcoatings with crosslinkable systems, and in any application thatrequires post-crosslinking of the polymer. Indeed, various modificationsof the invention in addition to those shown and described herein willbecome apparent to those skilled in the art from the foregoingdescription. Such modifications are also intended to fall within thescope of the appended claims. All patents and patent applications citedin the foregoing text are expressly incorporate herein by reference intheir entirety.

1. A golf ball comprising at least one layer formed from aninterpenetrating polymer network comprising: a first polymeric systemcomprising a prepolymer cured with a first curing agent, wherein theprepolymer comprises a reaction product of an isocyanate having terminalisocyanate groups, a blocking agent, and a polyol; and a secondpolymeric system comprising an acrylate resin and an initiator.
 2. Thegolf ball of claim 1, wherein the initiator comprises benzoyl peroxide,t-amyl peroxide, or mixtures thereof.
 3. The golf ball of claim 1,wherein at least about 95 percent or more of the terminal isocyanategroups are blocked.
 4. The golf ball of claim 1, wherein at least about97 percent or more of the terminal isocyanate groups are blocked.
 5. Thegolf ball of claim 1, wherein the blocking agent comprises linear andbranched alcohols; phenols and phenol derivatives; oximes; lactams;lactones; β-dicarbonyl compounds; hydroxamic acid esters; bisulfiteaddition compounds; hydroxylamines; esters of p-hydroxybenzoic acid;N-hydroxyphthalimide; N-hydroxysuccinimide; triazoles; substitutedimidazolines; tetrahydropyrimidines; caprolactones; or mixtures thereof.6. The golf ball of claim 5, wherein the blocking agent is selected fromthe group consisting of phenols, branched alcohols, methyl ethylketoxime, ε-caprolactam, β-caprolactone, and mixtures thereof.
 7. Thegolf ball of claim 1, wherein the first and second polymeric systems arenot bonded to each other.
 8. A golf ball comprising a core and a cover,wherein a portion of the golf ball is formed from an interpenetratingpolymer network comprising: a first polymeric system comprising anisocyanate having terminal isocyanate groups, a polyol, and a blocked,delayed action curative; and a second polymeric system comprising anacrylate resin and an initiator.
 9. The golf ball of claim 8, whereinthe first polymeric system is saturated.
 10. The golf ball of claim 8,wherein the first polymeric system further comprises a catalystcomprising an organometallic compound, tertiary amine, or combinationthereof.
 11. The golf ball of claim 8, wherein the blocked delayedaction curative comprises methylene dianiline and sodium chloride. 12.The golf ball of claim 8, wherein the initiator comprises benzoylperoxide, t-amyl peroxide, or mixtures thereof.
 13. The golf ball ofclaim 8, further comprising an intermediate layer.
 14. The golf ball ofclaim 13, wherein the portion comprises the cover.
 15. The golf ball ofclaim 8, wherein the blocked, delayed action curative has a deblockingtemperature of about 175° F. to about 350° F.
 16. A golf ball comprisinga core and a cover, wherein the cover comprises an interpenetratingpolymer network comprising: a first polymeric system comprising anisocyanate having terminal isocyanate groups, an isocyanate-reactivecomponent, and a curing agent, wherein the curing agent comprisesmethylene dianiline and sodium chloride; and a second polymeric systemcomprising an acrylate resin and an initiator, wherein the wherein thefirst and second polymeric systems are not bonded to each other.
 17. Thegolf ball of claim 16, wherein the first polymeric system is saturated.18. The golf ball of claim 16, wherein the initiator comprises benzoylperoxide, t-amyl peroxide, or mixtures thereof.
 19. The golf ball ofclaim 16, wherein the isocyanate-reactive component comprises ahydroxy-terminated compound.
 20. The golf ball of claim 16, wherein theisocyanate-reactive component comprises a amine-terminated compound.